Best Reverse Osmosis Systems (2026)

Under-sink tank systems, tankless units and countertop dispensers compared on official manufacturer specifications. Daily production is the maker's rated gallons per day, usually at a stated pressure. NSF/ANSI 58 is scored only when the official page names that standard; a WQA Gold Seal claim without a named standard is quoted and not scored as 58. Drain ratios are scored only when the maker's wording makes the direction clear, then converted to gallons of drain water per gallon of product water and labelled computed.

Updated 2026-11-1350 products compared6 scored criteriaHow this ranking works

Affiliate disclosure: We earn a commission if you buy through links on this page, at no extra cost to you. It never affects our rankings, which come from the published scoring formula. As an Amazon Associate I earn from qualifying purchases. Learn more.

Top pick

Waterdrop X16

Score 7.5/10 · Check price

Why it wins: 11-stage 1,600 GPD tankless RO, NSF/ANSI 42 and 58 named, 3:1 pure-to-drain. Top daily production in this comparison (1600 GPD).

Also great: Waterdrop X12 (6.9) · Waterdrop X12-PRO (6.9)

7.5/10

Check price at Amazon See pros, cons & specs

Side-by-side comparison

Swipe sideways on mobile. Green marks the best figure in each column.

Product	Score	Daily production	NSF/ANSI 58 named	Broader named certification	Drain water per product gallon	Best for	Price	Buy
1 W Waterdrop X16	7.5/10	1600 GPD	Yes	Yes	0.333 gal/gal	11-stage 1,600 GPD tankless RO, NSF/ANSI 42 and 58 named, 3:1 pure-to-drain	Check price	View deal
2 W Waterdrop X12	6.9/10	1200 GPD	Yes	Yes	0.333 gal/gal	11-stage 1,200 GPD tankless RO, NSF/ANSI 42 and 58 named, 3:1 pure-to-drain	Check price	View deal
3 W Waterdrop X12-PRO	6.9/10	1200 GPD	Yes	Yes	0.333 gal/gal	11-stage 1,200 GPD dual-flow tankless RO, NSF/ANSI 42 and 58 named	Check price	View deal
4 W Waterdrop X14	6.9/10	1400 GPD	Yes	Yes	Not listed	11-stage 1,400 GPD alkaline tankless RO, NSF/ANSI 42 and 58 named	Check price	View deal
5 W Waterdrop X8	6.1/10	800 GPD	Yes	Yes	0.5 gal/gal	9-stage 800 GPD tankless RO, NSF/ANSI 42 and 58 named, 2:1 pure-to-drain	Check price	View deal
6 W Waterdrop X8-PRO	6.0/10	800 GPD	Yes	Yes	Not listed	9-stage 800 GPD dual-flow tankless RO, NSF/ANSI 42 and 58 named	Check price	View deal
7 W Waterdrop G3P600	5.3/10	600 GPD	Yes	Yes	0.5 gal/gal	8-stage 600 GPD tankless RO, NSF/ANSI 42 and 58 named, 2:1 pure-to-drain	Check price	View deal
8 W Waterdrop G3P800	4.1/10	800 GPD	Yes	No	0.333 gal/gal	9-stage 800 GPD tankless RO with UV, NSF/ANSI 58 named, 3:1 pure-to-drain	Check price	View deal
9 I iSpring RCC7AK	4.1/10	75 GPD	Yes	Yes	Not listed	NSF/ANSI 58 certified 6-stage 75 GPD alkaline under-sink RO	Check price	View deal
10 A APEC ROTL-A1000ALK	3.8/10	1000 GPD	Yes	No	Not listed	5-stage 1000 GPD alkaline tankless RO, NSF/ANSI 58 and 372 named in the official title	Check price	View deal
11 A APEC ROTL-A1000	3.6/10	1000 GPD	Yes	No	Not listed	4-stage 1000 GPD tankless RO, NSF/ANSI 58 and 372 named in the official title	Check price	View deal
12 I iSpring RO500-BN	2.8/10	500 GPD	Yes	No	0.5 gal/gal	NSF/ANSI 58 certified 500 GPD tankless RO with a 2:1 pure-to-drain ratio	Check price	View deal
13 I iSpring RCC7AK-UV	2.6/10	75 GPD	Yes	No	Not listed	NSF/ANSI 58 certified 7-stage 75 GPD alkaline and UV under-sink RO	Check price	View deal
14 I iSpring RCC7U	2.5/10	75 GPD	Yes	No	Not listed	NSF/ANSI 58 certified 6-stage 75 GPD UV under-sink RO	Check price	View deal
15 I iSpring RCC7	2.3/10	75 GPD	Yes	No	Not listed	NSF/ANSI 58 certified 5-stage 75 GPD under-sink RO	Check price	View deal
16 A APEC RO-PH90	2.1/10	90 GPD	No	Yes	Not listed	6-stage 90 GPD alkaline under-sink RO with a named WQA contaminant list	Check price	View deal
17 A APEC RO-90	2.0/10	90 GPD	No	Yes	Not listed	5-stage 90 GPD under-sink RO with a named WQA contaminant list	Check price	View deal
18 W Waterdrop T4-A	1.8/10	450 GPD	No	No	0.5 gal/gal	450 GPD alkaline dual-flow under-sink RO with a 2:1 pure-to-drain ratio	Check price	View deal
19 I iSpring RO1200	1.8/10	1200 GPD	No	No	0.333 gal/gal	1,200 GPD dual-flow tankless RO with a 3:1 pure-to-drain ratio	Check price	View deal
20 W Waterdrop G5P700A	1.8/10	700 GPD	No	No	Not listed	8-stage 700 GPD alkaline tankless RO	Check price	View deal
21 W Waterdrop G5P700	1.7/10	700 GPD	No	No	0.5 gal/gal	7-stage 700 GPD tankless RO with a 2:1 pure-to-drain ratio	Check price	View deal
22 W Waterdrop T3-M	1.6/10	450 GPD	No	No	0.5 gal/gal	9-stage 450 GPD remineralizing under-sink RO with a 2:1 pure-to-drain ratio	Check price	View deal
23 W Waterdrop D6	1.5/10	600 GPD	No	No	0.667 gal/gal	6-stage 600 GPD tankless RO with a 1.5:1 pure-to-drain ratio	Check price	View deal
24 W Waterdrop G5P500	1.3/10	500 GPD	No	No	Not listed	7-stage 500 GPD tankless RO	Check price	View deal
25 I iSpring RO800G	1.2/10	800 GPD	No	No	0.4 gal/gal	800 GPD tankless RO with an up-to 2.5:1 pure-to-drain ratio	Check price	View deal
26 I iSpring RO600-BN	0.9/10	600 GPD	No	No	0.4 gal/gal	600 GPD tankless RO with a 2.5:1 pure-to-drain ratio	Check price	View deal
27 A APEC ROTL-600	0.9/10	600 GPD	No	No	Not listed	3-stage 600 GPD tankless under-sink RO	Check price	View deal
28 A APEC ROTL-AIO	0.9/10	600 GPD	No	No	Not listed	600 GPD all-in-one tankless under-sink RO	Check price	View deal
29 I iSpring RCC2AK-UV	0.8/10	200 GPD	No	No	Not listed	7-stage 200 GPD alkaline and UV under-sink RO	Check price	View deal
30 I iSpring RO5004F-AK	0.8/10	500 GPD	No	No	0.5 gal/gal	500 GPD alkaline tankless RO with UV and a 2:1 pure-to-drain ratio	Check price	View deal
31 I iSpring RCC1UP-AK	0.7/10	100 GPD	No	No	Not listed	7-stage 100 GPD alkaline under-sink RO with a booster pump and UV	Check price	View deal
32 I iSpring RCC2AK	0.7/10	200 GPD	No	No	Not listed	6-stage 200 GPD alkaline under-sink RO	Check price	View deal
33 A APEC ROES-PHUV75	0.6/10	75 GPD	No	No	Not listed	7-stage 75 GPD alkaline and UV under-sink RO	Check price	View deal
34 I iSpring PH100	0.5/10	100 GPD	No	No	Not listed	6-stage 100 GPD alkaline under-sink RO	Check price	View deal
35 I iSpring RCC2	0.5/10	200 GPD	No	No	Not listed	5-stage 200 GPD under-sink RO	Check price	View deal
36 A APEC ROES-PH75	0.5/10	75 GPD	No	No	Not listed	6-stage 75 GPD alkaline under-sink RO	Check price	View deal
37 A APEC ROES-UV75-SS	0.5/10	75 GPD	No	No	Not listed	6-stage 75 GPD UV under-sink RO with a stainless housing	Check price	View deal
38 I iSpring RCC1UP	0.5/10	100 GPD	No	No	Not listed	6-stage 100 GPD under-sink RO with a booster pump and UV	Check price	View deal
39 I iSpring RCD100	0.4/10	100 GPD	No	No	0.4 gal/gal	5-stage 100 GPD countertop RO with UV and a 2.5:1 pure-to-drain ratio	Check price	View deal
40 I iSpring RO100	0.4/10	100 GPD	No	No	Not listed	5-stage 100 GPD under-sink RO	Check price	View deal
41 A APEC RO-Hi	0.4/10	90 GPD	No	No	Not listed	5-stage 90 GPD fast-flow under-sink RO	Check price	View deal
42 A APEC RO-PERM	0.4/10	90 GPD	No	No	Not listed	5-stage 90 GPD under-sink RO with a permeate pump for low-pressure homes	Check price	View deal
43 A APEC ROES-100	0.4/10	100 GPD	No	No	Not listed	5-stage 100 GPD under-sink RO	Check price	View deal
44 I iSpring RCC100P	0.4/10	100 GPD	No	No	Not listed	5-stage 100 GPD under-sink RO with a booster pump	Check price	View deal
45 A APEC ROES-50	0.3/10	50 GPD	No	No	Not listed	5-stage 50 GPD under-sink RO with a 4-gallon tank	Check price	View deal
46 I iSpring RCC7P	0.3/10	75 GPD	No	No	Not listed	5-stage 75 GPD under-sink RO with a booster pump	Check price	View deal
47 A APEC RO-CTOP-C	0.2/10	90 GPD	No	No	Not listed	Portable 4-stage 90 GPD countertop RO with a carry case	Check price	View deal
48 A APEC RO-CTOP-PH	0.2/10	90 GPD	No	No	Not listed	Portable 4-stage 90 GPD alkaline countertop RO	Check price	View deal
49 A APEC RO-QUICK90	0.2/10	90 GPD	No	No	Not listed	Compact 4-stage 90 GPD under-sink RO	Check price	View deal
50 I iSpring RO10001F	0.0/10	Not listed	No	No	0.333 gal/gal	Tankless under-sink RO with a 3:1 pure-to-drain ratio and 0.69 GPM listed flow	Check price	View deal

"Not listed" means the manufacturer page we used does not publish that figure. Prices show "Check price" until a retailer feed provides a current price.

Every reverse osmosis system, ranked

#1 · Top pick

Waterdrop X16

Best for: 11-stage 1,600 GPD tankless RO, NSF/ANSI 42 and 58 named, 3:1 pure-to-drain

7.5/10

What we like

Top daily production in this comparison (1600 GPD)

Watch out for

Score breakdown

Daily production 24%

NSF/ANSI 58 named 20%

Broader named certification 16%

Drain water per product gallon 16%

Filtration stages 12%

Warranty 12%

Daily production	1600 GPD
NSF/ANSI 58 named	Yes
Broader named certification	Yes
Drain water per product gallon	0.333 gal/gal
Filtration stages	11
Warranty	2 yr
Daily production (maker)	1,600 gallons per day max capacity (official page)
Filtration stages (maker)	11 stages
NSF/ANSI 58 (maker)	Official page: NSF/ANSI 42&58&372 Certified
Broader named certification	Official page names an additional NSF/ANSI standard (for example 42 or 53) or certified reductions beyond TDS
Drain ratio (maker)	3:1 purified-water ratio (official page)
Drain water per product gallon	0.333 gal/gal (computed)
Warranty (maker)	2 years (official X-series pages)
Package weight (maker)	36.92 pounds
Price	Check price

Check price at Amazon Full specs

Specs source:

Waterdrop: X16

Waterdrop X12

Best for: 11-stage 1,200 GPD tankless RO, NSF/ANSI 42 and 58 named, 3:1 pure-to-drain

6.9/10

What we like

Watch out for

Score breakdown

Daily production 24%

NSF/ANSI 58 named 20%

Broader named certification 16%

Drain water per product gallon 16%

Filtration stages 12%

Warranty 12%

Daily production	1200 GPD
NSF/ANSI 58 named	Yes
Broader named certification	Yes
Drain water per product gallon	0.333 gal/gal
Filtration stages	11
Warranty	2 yr
Daily production (maker)	1,200 gallons per day
Filtration stages (maker)	11 stages
NSF/ANSI 58 (maker)	Official page: NSF/ANSI 42&58&372 Certified, with IAPMO R&T language against NSF/ANSI 58 on the performance data sheet
Broader named certification	Official page names an additional NSF/ANSI standard (for example 42 or 53) or certified reductions beyond TDS
Drain ratio (maker)	3:1 purified-water / pure-to-drain ratio (official page)
Drain water per product gallon	0.333 gal/gal (computed)
Warranty (maker)	2 years (official page)
Package weight (maker)	36.92 pounds
Reduced substances (maker)	Official page lists TDS, PFOA, PFOS, chlorine, fluoride, barium, arsenic, lead and others
Price	Check price

Check price at Amazon Full specs

Specs source:

Waterdrop: X12

Waterdrop X12-PRO

Best for: 11-stage 1,200 GPD dual-flow tankless RO, NSF/ANSI 42 and 58 named

6.9/10

What we like

Watch out for

Score breakdown

Daily production 24%

NSF/ANSI 58 named 20%

Broader named certification 16%

Drain water per product gallon 16%

Filtration stages 12%

Warranty 12%

Daily production	1200 GPD
NSF/ANSI 58 named	Yes
Broader named certification	Yes
Drain water per product gallon	0.333 gal/gal
Filtration stages	11
Warranty	2 yr
Daily production (maker)	1,200 gallons per day
Filtration stages (maker)	11 stages
NSF/ANSI 58 (maker)	Official page: certified by IAPMO R&T against NSF/ANSI Standard 42, 58
Broader named certification	Official page names an additional NSF/ANSI standard (for example 42 or 53) or certified reductions beyond TDS
Drain ratio (maker)	3:1 ratio language on the official X12-PRO page (pure-to-drain family wording)
Drain water per product gallon	0.333 gal/gal (computed)
Warranty (maker)	2-year warranty and lifetime technical support (official page)
Design (maker)	Dual-flow tankless
Price	Check price

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Specs source:

Waterdrop: X12-PRO

Waterdrop X14

Best for: 11-stage 1,400 GPD alkaline tankless RO, NSF/ANSI 42 and 58 named

6.9/10

What we like

Watch out for

Drain water per product gallon not published by Waterdrop
Warranty not published by Waterdrop

Score breakdown

Daily production 24%

NSF/ANSI 58 named 20%

Broader named certification 16%

Drain water per product gallon * 16%

Filtration stages 12%

Warranty * 12%

* Not published by the manufacturer; scored at the lowest published value in this category, so an unpublished figure never outranks a published one.

Daily production	1400 GPD
NSF/ANSI 58 named	Yes
Broader named certification	Yes
Drain water per product gallon	Not listed
Filtration stages	11
Warranty	Not listed
Daily production (maker)	1,400 gallons per day
Filtration stages (maker)	11 stages
NSF/ANSI 58 (maker)	Official page: NSF/ANSI 42 & 58 & 372 Certified
Broader named certification	Official page names an additional NSF/ANSI standard (for example 42 or 53) or certified reductions beyond TDS
Drain ratio (maker)	Not listed
Drain water per product gallon	Not listed
Warranty (maker)	Not listed
Alkaline stage (maker)	11-stage alkaline filtration (official page)
Price	Check price

Check price at Amazon Full specs

Specs source:

Waterdrop: X14

Waterdrop X8

Best for: 9-stage 800 GPD tankless RO, NSF/ANSI 42 and 58 named, 2:1 pure-to-drain

6.1/10

What we like

Watch out for

Score breakdown

Daily production 24%

NSF/ANSI 58 named 20%

Broader named certification 16%

Drain water per product gallon 16%

Filtration stages 12%

Warranty 12%

Daily production	800 GPD
NSF/ANSI 58 named	Yes
Broader named certification	Yes
Drain water per product gallon	0.5 gal/gal
Filtration stages	9
Warranty	2 yr
Daily production (maker)	800 gallons per day
Filtration stages (maker)	9 stages
NSF/ANSI 58 (maker)	Official page: NSF/ANSI 42 & 58 & 372 Certified
Broader named certification	Official page names an additional NSF/ANSI standard (for example 42 or 53) or certified reductions beyond TDS
Drain ratio (maker)	2:1 pure-to-drain ratio (official page)
Drain water per product gallon	0.5 gal/gal (computed)
Warranty (maker)	2-year warranty and lifetime technical support (official page)
Package weight (maker)	36.45 pounds
Price	Check price

Check price at Amazon Full specs

Specs source:

Waterdrop: X8

Waterdrop X8-PRO

Best for: 9-stage 800 GPD dual-flow tankless RO, NSF/ANSI 42 and 58 named

6.0/10

What we like

Watch out for

Drain water per product gallon not published by Waterdrop

Score breakdown

Daily production 24%

NSF/ANSI 58 named 20%

Broader named certification 16%

Drain water per product gallon * 16%

Filtration stages 12%

Warranty 12%

* Not published by the manufacturer; scored at the lowest published value in this category, so an unpublished figure never outranks a published one.

Daily production	800 GPD
NSF/ANSI 58 named	Yes
Broader named certification	Yes
Drain water per product gallon	Not listed
Filtration stages	9
Warranty	2 yr
Daily production (maker)	800 gallons per day (official compare table, X8-PRO column)
Filtration stages (maker)	9 stages
NSF/ANSI 58 (maker)	Official page: certified by IAPMO R&T against NSF/ANSI Standard 42, 58
Broader named certification	Official page names an additional NSF/ANSI standard (for example 42 or 53) or certified reductions beyond TDS
Drain ratio (maker)	Not listed
Drain water per product gallon	Not listed
Warranty (maker)	2-year warranty (official page)
Design (maker)	Dual-flow
Package weight (maker)	36.37 pounds
Price	Check price

Check price at Amazon Full specs

Specs source:

Waterdrop: X8-PRO

Waterdrop G3P600

Best for: 8-stage 600 GPD tankless RO, NSF/ANSI 42 and 58 named, 2:1 pure-to-drain

5.3/10

What we like

Watch out for

Warranty not published by Waterdrop

Score breakdown

Daily production 24%

NSF/ANSI 58 named 20%

Broader named certification 16%

Drain water per product gallon 16%

Filtration stages 12%

Warranty * 12%

* Not published by the manufacturer; scored at the lowest published value in this category, so an unpublished figure never outranks a published one.

Daily production	600 GPD
NSF/ANSI 58 named	Yes
Broader named certification	Yes
Drain water per product gallon	0.5 gal/gal
Filtration stages	8
Warranty	Not listed
Daily production (maker)	600 gallons per day
Filtration stages (maker)	8 stages
NSF/ANSI 58 (maker)	Official page headline: NSF/ANSI 42&58&372 Certified
Broader named certification	Official page names an additional NSF/ANSI standard (for example 42 or 53) or certified reductions beyond TDS
Drain ratio (maker)	2:1 pure-to-drain (official page: 2:1 Pure to Ratio / 2:1 pure-to-drain on the same official listing family)
Drain water per product gallon	0.5 gal/gal (computed)
Warranty (maker)	Not listed
Design (maker)	Tankless, smart display faucet
Package weight (maker)	32.4 pounds (official compare table on this product page)
Price	Check price

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Specs source:

Waterdrop: G3P600

Waterdrop G3P800

Best for: 9-stage 800 GPD tankless RO with UV, NSF/ANSI 58 named, 3:1 pure-to-drain

4.1/10

What we like

Watch out for

Warranty not published by Waterdrop

Score breakdown

Daily production 24%

NSF/ANSI 58 named 20%

Broader named certification 16%

Drain water per product gallon 16%

Filtration stages 12%

Warranty * 12%

* Not published by the manufacturer; scored at the lowest published value in this category, so an unpublished figure never outranks a published one.

Daily production	800 GPD
NSF/ANSI 58 named	Yes
Broader named certification	No
Drain water per product gallon	0.333 gal/gal
Filtration stages	9
Warranty	Not listed
Daily production (maker)	800 gallons per day (max daily production rate, official spec table)
Filtration stages (maker)	9 stages
NSF/ANSI 58 (maker)	Official page: NSF/ANSI 58 & 372 certified, including TDS reduction under 58
Broader named certification	Not listed as a broader named certification on the page we used
Drain ratio (maker)	3:1 drain ratio / 3:1 pure-to-drain (official page)
Drain water per product gallon	0.333 gal/gal (computed)
Warranty (maker)	Not listed
Design (maker)	Tankless with UV sterilizer
Size (maker)	18.06" x 5.65" x 17.75" (official table)
Price	Check price

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Specs source:

Waterdrop: G3P800

iSpring RCC7AK

Best for: NSF/ANSI 58 certified 6-stage 75 GPD alkaline under-sink RO

4.1/10

What we like

Watch out for

Drain water per product gallon not published by iSpring
Warranty not published by iSpring

Score breakdown

Daily production 24%

NSF/ANSI 58 named 20%

Broader named certification 16%

Drain water per product gallon * 16%

Filtration stages 12%

Warranty * 12%

* Not published by the manufacturer; scored at the lowest published value in this category, so an unpublished figure never outranks a published one.

Daily production	75 GPD
NSF/ANSI 58 named	Yes
Broader named certification	Yes
Drain water per product gallon	Not listed
Filtration stages	6
Warranty	Not listed
Daily production (maker)	75 gallons per day
Filtration stages (maker)	6 stages
NSF/ANSI 58 (maker)	Official title: NSF Certified; official page names NSF/ANSI 58 and lists certified reductions including asbestos, barium, cadmium, chromium, copper, fluoride, lead, selenium and TDS
Broader named certification	Official page names an additional NSF/ANSI standard (for example 42 or 53) or certified reductions beyond TDS
Drain ratio (maker)	Not listed
Drain water per product gallon	Not listed
Warranty (maker)	Not listed
Alkaline stage (maker)	6th-stage alkaline remineralization filter
Price	Check price

Check price at Amazon Full specs

Specs source:

iSpring: RCC7AK

#10

APEC ROTL-A1000ALK

Best for: 5-stage 1000 GPD alkaline tankless RO, NSF/ANSI 58 and 372 named in the official title

3.8/10

What we like

Watch out for

Drain water per product gallon not published by APEC
Warranty not published by APEC

Score breakdown

Daily production 24%

NSF/ANSI 58 named 20%

Broader named certification 16%

Drain water per product gallon * 16%

Filtration stages 12%

Warranty * 12%

* Not published by the manufacturer; scored at the lowest published value in this category, so an unpublished figure never outranks a published one.

Daily production	1000 GPD
NSF/ANSI 58 named	Yes
Broader named certification	No
Drain water per product gallon	Not listed
Filtration stages	5
Warranty	Not listed
Daily production (maker)	1,000 gallons per day (official product name)
Filtration stages (maker)	5 stages
NSF/ANSI 58 (maker)	Official product name: NSF 372 & 58 Certified
Broader named certification	Not listed as a broader named certification on the page we used
Drain ratio (maker)	Not listed
Drain water per product gallon	Not listed
Warranty (maker)	Not listed
Design (maker)	Alkaline tankless
NSF/ANSI 372 (maker)	Named in the official product title
Price	Check price

Check price at Amazon Full specs

Specs source:

APEC: ROTL-A1000ALK

#11

APEC ROTL-A1000

Best for: 4-stage 1000 GPD tankless RO, NSF/ANSI 58 and 372 named in the official title

3.6/10

What we like

Watch out for

Drain water per product gallon not published by APEC
Warranty not published by APEC

Score breakdown

Daily production 24%

NSF/ANSI 58 named 20%

Broader named certification 16%

Drain water per product gallon * 16%

Filtration stages 12%

Warranty * 12%

* Not published by the manufacturer; scored at the lowest published value in this category, so an unpublished figure never outranks a published one.

Daily production	1000 GPD
NSF/ANSI 58 named	Yes
Broader named certification	No
Drain water per product gallon	Not listed
Filtration stages	4
Warranty	Not listed
Daily production (maker)	1,000 gallons per day (official product name)
Filtration stages (maker)	4 stages
NSF/ANSI 58 (maker)	Official product name: NSF 372 & 58 Certified
Broader named certification	Not listed as a broader named certification on the page we used
Drain ratio (maker)	Not listed
Drain water per product gallon	Not listed
Warranty (maker)	Not listed
Design (maker)	Tankless
NSF/ANSI 372 (maker)	Named in the official product title (lead-free materials)
Price	Check price

Check price at Amazon Full specs

Specs source:

APEC: ROTL-A1000

#12

iSpring RO500-BN

Best for: NSF/ANSI 58 certified 500 GPD tankless RO with a 2:1 pure-to-drain ratio

2.8/10

What we like

Watch out for

Filtration stages not published by iSpring

Score breakdown

Daily production 24%

NSF/ANSI 58 named 20%

Broader named certification 16%

Drain water per product gallon 16%

Filtration stages * 12%

Warranty 12%

* Not published by the manufacturer; scored at the lowest published value in this category, so an unpublished figure never outranks a published one.

Daily production	500 GPD
NSF/ANSI 58 named	Yes
Broader named certification	No
Drain water per product gallon	0.5 gal/gal
Filtration stages	Not listed
Warranty	1 yr
Daily production (maker)	500 gallons per day
Filtration stages (maker)	Not listed
NSF/ANSI 58 (maker)	Official product name: NSF Certified; listing text names NSF 58
Broader named certification	Not listed as a broader named certification on the page we used
Drain ratio (maker)	2:1 pure-to-drain ratio (official product name)
Drain water per product gallon	0.5 gal/gal (computed)
Warranty (maker)	1-year manufacturer warranty
Design (maker)	Tankless, brushed nickel faucet
Price	Check price

Check price at Amazon Full specs

Specs source:

iSpring: RO500-BN

#13

iSpring RCC7AK-UV

Best for: NSF/ANSI 58 certified 7-stage 75 GPD alkaline and UV under-sink RO

2.6/10

What we like

Watch out for

Drain water per product gallon not published by iSpring
Warranty not published by iSpring

Score breakdown

Daily production 24%

NSF/ANSI 58 named 20%

Broader named certification 16%

Drain water per product gallon * 16%

Filtration stages 12%

Warranty * 12%

* Not published by the manufacturer; scored at the lowest published value in this category, so an unpublished figure never outranks a published one.

Daily production	75 GPD
NSF/ANSI 58 named	Yes
Broader named certification	No
Drain water per product gallon	Not listed
Filtration stages	7
Warranty	Not listed
Daily production (maker)	75 gallons per day
Filtration stages (maker)	7 stages
NSF/ANSI 58 (maker)	Official title: NSF Certified; collection listing names NSF/ANSI 58
Broader named certification	Not listed as a broader named certification on the page we used
Drain ratio (maker)	Not listed
Drain water per product gallon	Not listed
Warranty (maker)	Not listed
Alkaline and UV stages (maker)	7-stage system with alkaline remineralization and UV sterilizer
Price	Check price

Check price at Amazon Full specs

Specs source:

iSpring: RCC7AK-UV

#14

iSpring RCC7U

Best for: NSF/ANSI 58 certified 6-stage 75 GPD UV under-sink RO

2.5/10

What we like

Watch out for

Drain water per product gallon not published by iSpring
Warranty not published by iSpring

Score breakdown

Daily production 24%

NSF/ANSI 58 named 20%

Broader named certification 16%

Drain water per product gallon * 16%

Filtration stages 12%

Warranty * 12%

* Not published by the manufacturer; scored at the lowest published value in this category, so an unpublished figure never outranks a published one.

Daily production	75 GPD
NSF/ANSI 58 named	Yes
Broader named certification	No
Drain water per product gallon	Not listed
Filtration stages	6
Warranty	Not listed
Daily production (maker)	75 gallons per day
Filtration stages (maker)	6 stages
NSF/ANSI 58 (maker)	Official product name: NSF/ANSI 58 Certified
Broader named certification	Not listed as a broader named certification on the page we used
Drain ratio (maker)	Not listed
Drain water per product gallon	Not listed
Warranty (maker)	Not listed
UV stage (maker)	Listed as a 6-stage UV reverse osmosis system
Price	Check price

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Specs source:

iSpring: RCC7U

#15

iSpring RCC7

Best for: NSF/ANSI 58 certified 5-stage 75 GPD under-sink RO

2.3/10

What we like

Watch out for

Drain water per product gallon not published by iSpring
Warranty not published by iSpring

Score breakdown

Daily production 24%

NSF/ANSI 58 named 20%

Broader named certification 16%

Drain water per product gallon * 16%

Filtration stages 12%

Warranty * 12%

* Not published by the manufacturer; scored at the lowest published value in this category, so an unpublished figure never outranks a published one.

Daily production	75 GPD
NSF/ANSI 58 named	Yes
Broader named certification	No
Drain water per product gallon	Not listed
Filtration stages	5
Warranty	Not listed
Daily production (maker)	75 gallons per day (official product name and collection page)
Filtration stages (maker)	5 stages
NSF/ANSI 58 (maker)	Official title: NSF Certified; collection page names NSF/ANSI 58
Broader named certification	Not listed as a broader named certification on the page we used
Drain ratio (maker)	Not listed
Drain water per product gallon	Not listed
Warranty (maker)	Not listed
Membrane (maker)	Listed as reducing contaminants down to 0.0001 microns
Price	Check price

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Specs source:

iSpring: RCC7

#16

APEC RO-PH90

Best for: 6-stage 90 GPD alkaline under-sink RO with a named WQA contaminant list

2.1/10

What we like

Watch out for

Drain water per product gallon not published by APEC
Warranty not published by APEC

Score breakdown

Daily production 24%

NSF/ANSI 58 named 20%

Broader named certification 16%

Drain water per product gallon * 16%

Filtration stages 12%

Warranty * 12%

* Not published by the manufacturer; scored at the lowest published value in this category, so an unpublished figure never outranks a published one.

Daily production	90 GPD
NSF/ANSI 58 named	No
Broader named certification	Yes
Drain water per product gallon	Not listed
Filtration stages	6
Warranty	Not listed
Daily production (maker)	90 gallons per day @ 60 psi, 75 gallons/day @ 50 psi and 77 deg F
Filtration stages (maker)	6 stages
NSF/ANSI 58 (maker)	WQA Gold Seal Certified (NSF/ANSI 58 is not named on the page we used)
Broader named certification	Official page names an additional NSF/ANSI standard (for example 42 or 53) or certified reductions beyond TDS
Drain ratio (maker)	Not listed
Drain water per product gallon	Not listed
Warranty (maker)	Not listed
Tank capacity (maker)	4 gallons. 14 gallons optional
Alkaline stage (maker)	6th-stage mineral filter
Certified reductions (maker)	Official page says the system is certified to reduce Arsenic+3, Arsenic+5, Barium, Cadmium, Chromium-3, Chromium-6, Copper, Fluoride, Lead, Radioactivity, Selenium, and Turbidity
Price	Check price

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Specs source:

APEC: RO-PH90

#17

APEC RO-90

Best for: 5-stage 90 GPD under-sink RO with a named WQA contaminant list

2.0/10

What we like

Watch out for

Drain water per product gallon not published by APEC
Warranty not published by APEC

Score breakdown

Daily production 24%

NSF/ANSI 58 named 20%

Broader named certification 16%

Drain water per product gallon * 16%

Filtration stages 12%

Warranty * 12%

* Not published by the manufacturer; scored at the lowest published value in this category, so an unpublished figure never outranks a published one.

Daily production	90 GPD
NSF/ANSI 58 named	No
Broader named certification	Yes
Drain water per product gallon	Not listed
Filtration stages	5
Warranty	Not listed
Daily production (maker)	90 gallons per day @ 60 psi, 75 gallons/day @ 50 psi and 77 deg F
Filtration stages (maker)	5 stages
NSF/ANSI 58 (maker)	WQA Gold Seal Certified (NSF/ANSI 58 is not named on the page we used)
Broader named certification	Official page names an additional NSF/ANSI standard (for example 42 or 53) or certified reductions beyond TDS
Drain ratio (maker)	Not listed
Drain water per product gallon	Not listed
Warranty (maker)	Not listed
Tank capacity (maker)	4 gallons. 14 gallons optional
Certified reductions (maker)	Official page says the system is certified to reduce Arsenic+3, Arsenic+5, Barium, Cadmium, Chromium-3, Chromium-6, Copper, Fluoride, Lead, Radioactivity, Selenium, and Turbidity
Package weight (maker)	25 lbs
Feed water pressure (maker)	40-85 psi
Price	Check price

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Specs source:

APEC: RO-90

#18

Waterdrop T4-A

Best for: 450 GPD alkaline dual-flow under-sink RO with a 2:1 pure-to-drain ratio

1.8/10

What we like

Watch out for

Warranty not published by Waterdrop

Score breakdown

Daily production 24%

NSF/ANSI 58 named 20%

Broader named certification 16%

Drain water per product gallon 16%

Filtration stages 12%

Warranty * 12%

* Not published by the manufacturer; scored at the lowest published value in this category, so an unpublished figure never outranks a published one.

Daily production	450 GPD
NSF/ANSI 58 named	No
Broader named certification	No
Drain water per product gallon	0.5 gal/gal
Filtration stages	10
Warranty	Not listed
Daily production (maker)	450 gallons per day (official product name)
Filtration stages (maker)	10 stages
NSF/ANSI 58 (maker)	Official compare table lists NSF/ANSI 372 for this model, not NSF/ANSI 58
Broader named certification	Not listed as a broader named certification on the page we used
Drain ratio (maker)	2:1 pure-to-drain (official page)
Drain water per product gallon	0.5 gal/gal (computed)
Warranty (maker)	Not listed
Alkaline stage (maker)	Alkaline dual-flow system
Stages (maker)	10 stages in the official compare table, T4-A column
Package weight (maker)	24.25 pounds
Price	Check price

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Specs source:

Waterdrop: T4-A

#19

iSpring RO1200

Best for: 1,200 GPD dual-flow tankless RO with a 3:1 pure-to-drain ratio

1.8/10

What we like

Watch out for

Filtration stages not published by iSpring
Warranty not published by iSpring

Score breakdown

Daily production 24%

NSF/ANSI 58 named 20%

Broader named certification 16%

Drain water per product gallon 16%

Filtration stages * 12%

Warranty * 12%

* Not published by the manufacturer; scored at the lowest published value in this category, so an unpublished figure never outranks a published one.

Daily production	1200 GPD
NSF/ANSI 58 named	No
Broader named certification	No
Drain water per product gallon	0.333 gal/gal
Filtration stages	Not listed
Warranty	Not listed
Daily production (maker)	1,200 gallons per day
Filtration stages (maker)	Not listed
NSF/ANSI 58 (maker)	Not listed
Broader named certification	Not listed as a broader named certification on the page we used
Drain ratio (maker)	3:1 pure-to-drain (official product name)
Drain water per product gallon	0.333 gal/gal (computed)
Warranty (maker)	Not listed
Listed flow (maker)	0.83 GPM (official page)
Design (maker)	Dual-flow tankless, auto flush, TDS monitor
Price	Check price

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Specs source:

iSpring: RO1200

#20

Waterdrop G5P700A

Best for: 8-stage 700 GPD alkaline tankless RO

1.8/10

What we like

Watch out for

Drain water per product gallon not published by Waterdrop
Warranty not published by Waterdrop

Score breakdown

Daily production 24%

NSF/ANSI 58 named 20%

Broader named certification 16%

Drain water per product gallon * 16%

Filtration stages 12%

Warranty * 12%

* Not published by the manufacturer; scored at the lowest published value in this category, so an unpublished figure never outranks a published one.

Daily production	700 GPD
NSF/ANSI 58 named	No
Broader named certification	No
Drain water per product gallon	Not listed
Filtration stages	8
Warranty	Not listed
Daily production (maker)	700 gallons per day
Filtration stages (maker)	8 stages
NSF/ANSI 58 (maker)	Official compare table lists NSF/ANSI 372 for this model, not NSF/ANSI 58
Broader named certification	Not listed as a broader named certification on the page we used
Drain ratio (maker)	Not listed
Drain water per product gallon	Not listed
Warranty (maker)	Not listed
Alkaline stage (maker)	8-stage filtration with added minerals (official page)
Package weight (maker)	26 pounds
Price	Check price

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Specs source:

Waterdrop: G5P700A

#21

Waterdrop G5P700

Best for: 7-stage 700 GPD tankless RO with a 2:1 pure-to-drain ratio

1.7/10

What we like

Watch out for

Score breakdown

Daily production 24%

NSF/ANSI 58 named 20%

Broader named certification 16%

Drain water per product gallon 16%

Filtration stages 12%

Warranty 12%

Daily production	700 GPD
NSF/ANSI 58 named	No
Broader named certification	No
Drain water per product gallon	0.5 gal/gal
Filtration stages	7
Warranty	1 yr
Daily production (maker)	700 gallons per day
Filtration stages (maker)	7 stages
NSF/ANSI 58 (maker)	Official compare table lists NSF/ANSI 372 for this model, not NSF/ANSI 58
Broader named certification	Not listed as a broader named certification on the page we used
Drain ratio (maker)	2:1 pure-to-drain rate (official compare table, G5P700 column)
Drain water per product gallon	0.5 gal/gal (computed)
Warranty (maker)	1 year (official compare table)
Package weight (maker)	26 pounds
Price	Check price

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Specs source:

Waterdrop: G5P700

#22

Waterdrop T3-M

Best for: 9-stage 450 GPD remineralizing under-sink RO with a 2:1 pure-to-drain ratio

1.6/10

What we like

Watch out for

Warranty not published by Waterdrop

Score breakdown

Daily production 24%

NSF/ANSI 58 named 20%

Broader named certification 16%

Drain water per product gallon 16%

Filtration stages 12%

Warranty * 12%

* Not published by the manufacturer; scored at the lowest published value in this category, so an unpublished figure never outranks a published one.

Daily production	450 GPD
NSF/ANSI 58 named	No
Broader named certification	No
Drain water per product gallon	0.5 gal/gal
Filtration stages	9
Warranty	Not listed
Daily production (maker)	450 gallons per day
Filtration stages (maker)	9 stages
NSF/ANSI 58 (maker)	Not listed
Broader named certification	Not listed as a broader named certification on the page we used
Drain ratio (maker)	2:1 pure-to-drain ratio (official page)
Drain water per product gallon	0.5 gal/gal (computed)
Warranty (maker)	Not listed
Alkaline stage (maker)	Remineralization RO
RO filter life (maker)	24-month RO filter lifespan (official page)
Price	Check price

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Specs source:

Waterdrop: T3-M

#23

Waterdrop D6

Best for: 6-stage 600 GPD tankless RO with a 1.5:1 pure-to-drain ratio

1.5/10

What we like

Watch out for

Highest drain water per product gallon in this comparison (0.667 gal/gal)
Warranty not published by Waterdrop

Score breakdown

Daily production 24%

NSF/ANSI 58 named 20%

Broader named certification 16%

Drain water per product gallon 16%

Filtration stages 12%

Warranty * 12%

* Not published by the manufacturer; scored at the lowest published value in this category, so an unpublished figure never outranks a published one.

Daily production	600 GPD
NSF/ANSI 58 named	No
Broader named certification	No
Drain water per product gallon	0.667 gal/gal
Filtration stages	6
Warranty	Not listed
Daily production (maker)	600 gallons per day
Filtration stages (maker)	6 stages
NSF/ANSI 58 (maker)	Not listed
Broader named certification	Not listed as a broader named certification on the page we used
Drain ratio (maker)	1.5:1 pure-to-drain (official page)
Drain water per product gallon	0.667 gal/gal (computed)
Warranty (maker)	Not listed
Design (maker)	Tankless, smart faucet
Package weight (maker)	22.2 pounds
Dimensions (maker)	15.98 x 5.98 x 11.97 inches
Price	Check price

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Specs source:

Waterdrop: D6

#24

Waterdrop G5P500

Best for: 7-stage 500 GPD tankless RO

1.3/10

What we like

Watch out for

Drain water per product gallon not published by Waterdrop
Warranty not published by Waterdrop

Score breakdown

Daily production 24%

NSF/ANSI 58 named 20%

Broader named certification 16%

Drain water per product gallon * 16%

Filtration stages 12%

Warranty * 12%

* Not published by the manufacturer; scored at the lowest published value in this category, so an unpublished figure never outranks a published one.

Daily production	500 GPD
NSF/ANSI 58 named	No
Broader named certification	No
Drain water per product gallon	Not listed
Filtration stages	7
Warranty	Not listed
Daily production (maker)	500 gallons per day
Filtration stages (maker)	7 stages
NSF/ANSI 58 (maker)	Official compare table on sibling pages lists NSF/ANSI 372 for the G5 family; this product page does not name NSF/ANSI 58 for the G5P500 itself in a standalone sentence we used
Broader named certification	Not listed as a broader named certification on the page we used
Drain ratio (maker)	Not listed
Drain water per product gallon	Not listed
Warranty (maker)	Not listed
Design (maker)	Tankless
Package weight (maker)	24.8 pounds (official page)
Price	Check price

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Specs source:

Waterdrop: G5P500

#25

iSpring RO800G

Best for: 800 GPD tankless RO with an up-to 2.5:1 pure-to-drain ratio

1.2/10

What we like

Watch out for

Filtration stages not published by iSpring
Warranty not published by iSpring

Score breakdown

Daily production 24%

NSF/ANSI 58 named 20%

Broader named certification 16%

Drain water per product gallon 16%

Filtration stages * 12%

Warranty * 12%

* Not published by the manufacturer; scored at the lowest published value in this category, so an unpublished figure never outranks a published one.

Daily production	800 GPD
NSF/ANSI 58 named	No
Broader named certification	No
Drain water per product gallon	0.4 gal/gal
Filtration stages	Not listed
Warranty	Not listed
Daily production (maker)	800 gallons per day
Filtration stages (maker)	Not listed
NSF/ANSI 58 (maker)	Not listed
Broader named certification	Not listed as a broader named certification on the page we used
Drain ratio (maker)	Up to 2.5:1 pure-to-drain ratio (official product name)
Drain water per product gallon	0.4 gal/gal (computed)
Warranty (maker)	Not listed
Design (maker)	Tankless
Price	Check price

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Specs source:

iSpring: RO800G

#26

iSpring RO600-BN

Best for: 600 GPD tankless RO with a 2.5:1 pure-to-drain ratio

0.9/10

What we like

Watch out for

Filtration stages not published by iSpring

Score breakdown

Daily production 24%

NSF/ANSI 58 named 20%

Broader named certification 16%

Drain water per product gallon 16%

Filtration stages * 12%

Warranty 12%

* Not published by the manufacturer; scored at the lowest published value in this category, so an unpublished figure never outranks a published one.

Daily production	600 GPD
NSF/ANSI 58 named	No
Broader named certification	No
Drain water per product gallon	0.4 gal/gal
Filtration stages	Not listed
Warranty	1 yr
Daily production (maker)	600 gallons per day
Filtration stages (maker)	Not listed
NSF/ANSI 58 (maker)	Not listed
Broader named certification	Not listed as a broader named certification on the page we used
Drain ratio (maker)	2.5:1 pure-to-drain ratio (official product name)
Drain water per product gallon	0.4 gal/gal (computed)
Warranty (maker)	1-year limited manufacturer warranty
Design (maker)	Tankless
Listed flow (maker)	Up to 0.4 GPM (official page)
Price	Check price

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Specs source:

iSpring: RO600-BN

#27

APEC ROTL-600

Best for: 3-stage 600 GPD tankless under-sink RO

0.9/10

What we like

Watch out for

Drain water per product gallon not published by APEC
Lowest filtration stages in this comparison (3)
Warranty not published by APEC

Score breakdown

Daily production 24%

NSF/ANSI 58 named 20%

Broader named certification 16%

Drain water per product gallon * 16%

Filtration stages 12%

Warranty * 12%

* Not published by the manufacturer; scored at the lowest published value in this category, so an unpublished figure never outranks a published one.

Daily production	600 GPD
NSF/ANSI 58 named	No
Broader named certification	No
Drain water per product gallon	Not listed
Filtration stages	3
Warranty	Not listed
Daily production (maker)	600 gallons per day @ 60 psi
Filtration stages (maker)	3 stages
NSF/ANSI 58 (maker)	Not listed
Broader named certification	Not listed as a broader named certification on the page we used
Drain ratio (maker)	Not listed
Drain water per product gallon	Not listed
Warranty (maker)	Not listed
Design (maker)	Tankless
Feed water pressure (maker)	30-100 psi
Package weight (maker)	30 lbs
Price	Check price

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Specs source:

APEC: ROTL-600

#28

APEC ROTL-AIO

Best for: 600 GPD all-in-one tankless under-sink RO

0.9/10

What we like

Watch out for

Drain water per product gallon not published by APEC
Filtration stages not published by APEC
Warranty not published by APEC

Score breakdown

Daily production 24%

NSF/ANSI 58 named 20%

Broader named certification 16%

Drain water per product gallon * 16%

Filtration stages * 12%

Warranty * 12%

* Not published by the manufacturer; scored at the lowest published value in this category, so an unpublished figure never outranks a published one.

Daily production	600 GPD
NSF/ANSI 58 named	No
Broader named certification	No
Drain water per product gallon	Not listed
Filtration stages	Not listed
Warranty	Not listed
Daily production (maker)	600 gallons per day @ 60 psi
Filtration stages (maker)	Not listed
NSF/ANSI 58 (maker)	Not listed
Broader named certification	Not listed as a broader named certification on the page we used
Drain ratio (maker)	Not listed
Drain water per product gallon	Not listed
Warranty (maker)	Not listed
Design (maker)	All-in-one tankless
Feed water pressure (maker)	30-100 psi
Package weight (maker)	20 lbs
Price	Check price

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Specs source:

APEC: ROTL-AIO

#29

iSpring RCC2AK-UV

Best for: 7-stage 200 GPD alkaline and UV under-sink RO

0.8/10

What we like

Watch out for

Drain water per product gallon not published by iSpring
Warranty not published by iSpring

Score breakdown

Daily production 24%

NSF/ANSI 58 named 20%

Broader named certification 16%

Drain water per product gallon * 16%

Filtration stages 12%

Warranty * 12%

* Not published by the manufacturer; scored at the lowest published value in this category, so an unpublished figure never outranks a published one.

Daily production	200 GPD
NSF/ANSI 58 named	No
Broader named certification	No
Drain water per product gallon	Not listed
Filtration stages	7
Warranty	Not listed
Daily production (maker)	200 gallons per day
Filtration stages (maker)	7 stages
NSF/ANSI 58 (maker)	Not listed
Broader named certification	Not listed as a broader named certification on the page we used
Drain ratio (maker)	Not listed
Drain water per product gallon	Not listed
Warranty (maker)	Not listed
Alkaline and UV stages (maker)	7-stage system with alkaline and ultraviolet filters
Price	Check price

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Specs source:

iSpring: RCC2AK-UV

#30

iSpring RO5004F-AK

Best for: 500 GPD alkaline tankless RO with UV and a 2:1 pure-to-drain ratio

0.8/10

What we like

Watch out for

Filtration stages not published by iSpring
Warranty not published by iSpring

Score breakdown

Daily production 24%

NSF/ANSI 58 named 20%

Broader named certification 16%

Drain water per product gallon 16%

Filtration stages * 12%

Warranty * 12%

* Not published by the manufacturer; scored at the lowest published value in this category, so an unpublished figure never outranks a published one.

Daily production	500 GPD
NSF/ANSI 58 named	No
Broader named certification	No
Drain water per product gallon	0.5 gal/gal
Filtration stages	Not listed
Warranty	Not listed
Daily production (maker)	500 gallons per day
Filtration stages (maker)	Not listed
NSF/ANSI 58 (maker)	Not listed
Broader named certification	Not listed as a broader named certification on the page we used
Drain ratio (maker)	2:1 pure-to-drain (official product name)
Drain water per product gallon	0.5 gal/gal (computed)
Warranty (maker)	Not listed
Design (maker)	Tankless with boost pump, UV and alkaline remineralization
Price	Check price

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Specs source:

iSpring: RO5004F-AK

#31

iSpring RCC1UP-AK

Best for: 7-stage 100 GPD alkaline under-sink RO with a booster pump and UV

0.7/10

What we like

Watch out for

Drain water per product gallon not published by iSpring
Warranty not published by iSpring

Score breakdown

Daily production 24%

NSF/ANSI 58 named 20%

Broader named certification 16%

Drain water per product gallon * 16%

Filtration stages 12%

Warranty * 12%

* Not published by the manufacturer; scored at the lowest published value in this category, so an unpublished figure never outranks a published one.

Daily production	100 GPD
NSF/ANSI 58 named	No
Broader named certification	No
Drain water per product gallon	Not listed
Filtration stages	7
Warranty	Not listed
Daily production (maker)	100 gallons per day
Filtration stages (maker)	7 stages
NSF/ANSI 58 (maker)	Not listed
Broader named certification	Not listed as a broader named certification on the page we used
Drain ratio (maker)	Not listed
Drain water per product gallon	Not listed
Warranty (maker)	Not listed
Price	Check price

Check price at Amazon Full specs

Specs source:

iSpring: RCC1UP-AK

#32

iSpring RCC2AK

Best for: 6-stage 200 GPD alkaline under-sink RO

0.7/10

What we like

Watch out for

Drain water per product gallon not published by iSpring
Warranty not published by iSpring

Score breakdown

Daily production 24%

NSF/ANSI 58 named 20%

Broader named certification 16%

Drain water per product gallon * 16%

Filtration stages 12%

Warranty * 12%

* Not published by the manufacturer; scored at the lowest published value in this category, so an unpublished figure never outranks a published one.

Daily production	200 GPD
NSF/ANSI 58 named	No
Broader named certification	No
Drain water per product gallon	Not listed
Filtration stages	6
Warranty	Not listed
Daily production (maker)	200 gallons per day
Filtration stages (maker)	6 stages
NSF/ANSI 58 (maker)	Not listed
Broader named certification	Not listed as a broader named certification on the page we used
Drain ratio (maker)	Not listed
Drain water per product gallon	Not listed
Warranty (maker)	Not listed
Alkaline stage (maker)	Alkaline remineralization filter
Price	Check price

Check price at Amazon Full specs

Specs source:

iSpring: RCC2AK

#33

APEC ROES-PHUV75

Best for: 7-stage 75 GPD alkaline and UV under-sink RO

0.6/10

What we like

Watch out for

Drain water per product gallon not published by APEC
Warranty not published by APEC

Score breakdown

Daily production 24%

NSF/ANSI 58 named 20%

Broader named certification 16%

Drain water per product gallon * 16%

Filtration stages 12%

Warranty * 12%

* Not published by the manufacturer; scored at the lowest published value in this category, so an unpublished figure never outranks a published one.

Daily production	75 GPD
NSF/ANSI 58 named	No
Broader named certification	No
Drain water per product gallon	Not listed
Filtration stages	7
Warranty	Not listed
Daily production (maker)	75 gallons per day @ 60 psi and 77 deg F
Filtration stages (maker)	7 stages
NSF/ANSI 58 (maker)	Not listed
Broader named certification	Not listed as a broader named certification on the page we used
Drain ratio (maker)	Not listed
Drain water per product gallon	Not listed
Warranty (maker)	Not listed
Tank capacity (maker)	4 gallons
UV stage (maker)	5th-stage UV sterilizer, listed as destroying up to 99.99% of bacteria, viruses and cysts
Package weight (maker)	27 lbs
Price	Check price

Check price at Amazon Full specs

Specs source:

APEC: ROES-PHUV75

#34

iSpring PH100

Best for: 6-stage 100 GPD alkaline under-sink RO

0.5/10

What we like

Watch out for

Drain water per product gallon not published by iSpring

Score breakdown

Daily production 24%

NSF/ANSI 58 named 20%

Broader named certification 16%

Drain water per product gallon * 16%

Filtration stages 12%

Warranty 12%

* Not published by the manufacturer; scored at the lowest published value in this category, so an unpublished figure never outranks a published one.

Daily production	100 GPD
NSF/ANSI 58 named	No
Broader named certification	No
Drain water per product gallon	Not listed
Filtration stages	6
Warranty	1 yr
Daily production (maker)	100 gallons per day
Filtration stages (maker)	6 stages
NSF/ANSI 58 (maker)	Not listed
Broader named certification	Not listed as a broader named certification on the page we used
Drain ratio (maker)	Not listed
Drain water per product gallon	Not listed
Warranty (maker)	1-year manufacturer warranty (official page)
Alkaline stage (maker)	Alkaline remineralization
Price	Check price

Check price at Amazon Full specs

Specs source:

iSpring: PH100

#35

iSpring RCC2

Best for: 5-stage 200 GPD under-sink RO

0.5/10

What we like

Watch out for

Drain water per product gallon not published by iSpring

Score breakdown

Daily production 24%

NSF/ANSI 58 named 20%

Broader named certification 16%

Drain water per product gallon * 16%

Filtration stages 12%

Warranty 12%

* Not published by the manufacturer; scored at the lowest published value in this category, so an unpublished figure never outranks a published one.

Daily production	200 GPD
NSF/ANSI 58 named	No
Broader named certification	No
Drain water per product gallon	Not listed
Filtration stages	5
Warranty	1 yr
Daily production (maker)	200 gallons per day
Filtration stages (maker)	5 stages
NSF/ANSI 58 (maker)	Not listed
Broader named certification	Not listed as a broader named certification on the page we used
Drain ratio (maker)	Not listed
Drain water per product gallon	Not listed
Warranty (maker)	1-year manufacturer warranty (official page)
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Specs source:

iSpring: RCC2

#36

APEC ROES-PH75

Best for: 6-stage 75 GPD alkaline under-sink RO

0.5/10

What we like

Watch out for

Drain water per product gallon not published by APEC
Warranty not published by APEC

Score breakdown

Daily production 24%

NSF/ANSI 58 named 20%

Broader named certification 16%

Drain water per product gallon * 16%

Filtration stages 12%

Warranty * 12%

* Not published by the manufacturer; scored at the lowest published value in this category, so an unpublished figure never outranks a published one.

Daily production	75 GPD
NSF/ANSI 58 named	No
Broader named certification	No
Drain water per product gallon	Not listed
Filtration stages	6
Warranty	Not listed
Daily production (maker)	75 gallons per day @ 60 psi and 77 deg F
Filtration stages (maker)	6 stages
NSF/ANSI 58 (maker)	WQA Certified (standard not named on the page we used)
Broader named certification	Not listed as a broader named certification on the page we used
Drain ratio (maker)	Not listed
Drain water per product gallon	Not listed
Warranty (maker)	Not listed
Tank capacity (maker)	4 gallons
Alkaline stage (maker)	6th-stage calcite remineralizing filter
Feed water pressure (maker)	40-85 psi
Package weight (maker)	27 lbs
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Specs source:

APEC: ROES-PH75

#37

APEC ROES-UV75-SS

Best for: 6-stage 75 GPD UV under-sink RO with a stainless housing

0.5/10

What we like

Watch out for

Drain water per product gallon not published by APEC
Warranty not published by APEC

Score breakdown

Daily production 24%

NSF/ANSI 58 named 20%

Broader named certification 16%

Drain water per product gallon * 16%

Filtration stages 12%

Warranty * 12%

* Not published by the manufacturer; scored at the lowest published value in this category, so an unpublished figure never outranks a published one.

Daily production	75 GPD
NSF/ANSI 58 named	No
Broader named certification	No
Drain water per product gallon	Not listed
Filtration stages	6
Warranty	Not listed
Daily production (maker)	75 gallons per day @ 60 psi and 77 deg F
Filtration stages (maker)	6 stages
NSF/ANSI 58 (maker)	Not listed
Broader named certification	Not listed as a broader named certification on the page we used
Drain ratio (maker)	Not listed
Drain water per product gallon	Not listed
Warranty (maker)	Not listed
Tank capacity (maker)	4 gallons
UV stage (maker)	5th-stage UV, listed as destroying up to 99.99% of bacteria, viruses and cysts
Package weight (maker)	27 lbs
System dimensions (maker)	The specification row labelled System Dimensions on this page shows 2.0-11.0, which matches the pH range on sibling pages, so we treat dimensions as not clearly listed
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Specs source:

APEC: ROES-UV75-SS

#38

iSpring RCC1UP

Best for: 6-stage 100 GPD under-sink RO with a booster pump and UV

0.5/10

What we like

Watch out for

Drain water per product gallon not published by iSpring
Warranty not published by iSpring

Score breakdown

Daily production 24%

NSF/ANSI 58 named 20%

Broader named certification 16%

Drain water per product gallon * 16%

Filtration stages 12%

Warranty * 12%

* Not published by the manufacturer; scored at the lowest published value in this category, so an unpublished figure never outranks a published one.

Daily production	100 GPD
NSF/ANSI 58 named	No
Broader named certification	No
Drain water per product gallon	Not listed
Filtration stages	6
Warranty	Not listed
Daily production (maker)	100 gallons per day
Filtration stages (maker)	6 stages
NSF/ANSI 58 (maker)	Not listed
Broader named certification	Not listed as a broader named certification on the page we used
Drain ratio (maker)	Not listed
Drain water per product gallon	Not listed
Warranty (maker)	Not listed
Pump and UV (maker)	Officially includes a booster pump and UV light sterilizer
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Specs source:

iSpring: RCC1UP

#39

iSpring RCD100

Best for: 5-stage 100 GPD countertop RO with UV and a 2.5:1 pure-to-drain ratio

0.4/10

What we like

Watch out for

Warranty not published by iSpring

Score breakdown

Daily production 24%

NSF/ANSI 58 named 20%

Broader named certification 16%

Drain water per product gallon 16%

Filtration stages 12%

Warranty * 12%

* Not published by the manufacturer; scored at the lowest published value in this category, so an unpublished figure never outranks a published one.

Daily production	100 GPD
NSF/ANSI 58 named	No
Broader named certification	No
Drain water per product gallon	0.4 gal/gal
Filtration stages	5
Warranty	Not listed
Daily production (maker)	100 gallons per day (official product name)
Filtration stages (maker)	5 stages
NSF/ANSI 58 (maker)	Not listed
Broader named certification	Not listed as a broader named certification on the page we used
Drain ratio (maker)	2.5:1 pure-to-drain (official product name)
Drain water per product gallon	0.4 gal/gal (computed)
Warranty (maker)	Not listed
Design (maker)	Countertop instant-hot dispenser with UV
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Specs source:

iSpring: RCD100

#40

iSpring RO100

Best for: 5-stage 100 GPD under-sink RO

0.4/10

What we like

Watch out for

Drain water per product gallon not published by iSpring

Score breakdown

Daily production 24%

NSF/ANSI 58 named 20%

Broader named certification 16%

Drain water per product gallon * 16%

Filtration stages 12%

Warranty 12%

* Not published by the manufacturer; scored at the lowest published value in this category, so an unpublished figure never outranks a published one.

Daily production	100 GPD
NSF/ANSI 58 named	No
Broader named certification	No
Drain water per product gallon	Not listed
Filtration stages	5
Warranty	1 yr
Daily production (maker)	100 gallons per day
Filtration stages (maker)	5 stages
NSF/ANSI 58 (maker)	Not listed
Broader named certification	Not listed as a broader named certification on the page we used
Drain ratio (maker)	Not listed
Drain water per product gallon	Not listed
Warranty (maker)	1-year manufacturer warranty (official page)
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Specs source:

iSpring: RO100

#41

APEC RO-Hi

Best for: 5-stage 90 GPD fast-flow under-sink RO

0.4/10

What we like

Watch out for

Drain water per product gallon not published by APEC
Warranty not published by APEC

Score breakdown

Daily production 24%

NSF/ANSI 58 named 20%

Broader named certification 16%

Drain water per product gallon * 16%

Filtration stages 12%

Warranty * 12%

* Not published by the manufacturer; scored at the lowest published value in this category, so an unpublished figure never outranks a published one.

Daily production	90 GPD
NSF/ANSI 58 named	No
Broader named certification	No
Drain water per product gallon	Not listed
Filtration stages	5
Warranty	Not listed
Daily production (maker)	90 gallons per day @ 60 psi, 75 gallons/day @ 50 psi and 77 deg F
Filtration stages (maker)	5 stages
NSF/ANSI 58 (maker)	WQA Certified (standard not named on the page we used)
Broader named certification	Not listed as a broader named certification on the page we used
Drain ratio (maker)	Not listed
Drain water per product gallon	Not listed
Warranty (maker)	Not listed
Tank capacity (maker)	4 gallons. 14 gallons optional
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Specs source:

APEC: RO-Hi

#42

APEC RO-PERM

Best for: 5-stage 90 GPD under-sink RO with a permeate pump for low-pressure homes

0.4/10

What we like

Watch out for

Drain water per product gallon not published by APEC
Warranty not published by APEC

Score breakdown

Daily production 24%

NSF/ANSI 58 named 20%

Broader named certification 16%

Drain water per product gallon * 16%

Filtration stages 12%

Warranty * 12%

* Not published by the manufacturer; scored at the lowest published value in this category, so an unpublished figure never outranks a published one.

Daily production	90 GPD
NSF/ANSI 58 named	No
Broader named certification	No
Drain water per product gallon	Not listed
Filtration stages	5
Warranty	Not listed
Daily production (maker)	90 gallons per day (Ultimate permeate-pumped system; official specification table lists the same 60 psi rating family as other Ultimate 90 GPD models)
Filtration stages (maker)	5 stages
NSF/ANSI 58 (maker)	Not listed
Broader named certification	Not listed as a broader named certification on the page we used
Drain ratio (maker)	Not listed
Drain water per product gallon	Not listed
Warranty (maker)	Not listed
Pump (maker)	Permeate pump, officially positioned for low inlet pressure
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Specs source:

APEC: RO-PERM

#43

APEC ROES-100

Best for: 5-stage 100 GPD under-sink RO

0.4/10

What we like

Watch out for

Drain water per product gallon not published by APEC
Warranty not published by APEC

Score breakdown

Daily production 24%

NSF/ANSI 58 named 20%

Broader named certification 16%

Drain water per product gallon * 16%

Filtration stages 12%

Warranty * 12%

* Not published by the manufacturer; scored at the lowest published value in this category, so an unpublished figure never outranks a published one.

Daily production	100 GPD
NSF/ANSI 58 named	No
Broader named certification	No
Drain water per product gallon	Not listed
Filtration stages	5
Warranty	Not listed
Daily production (maker)	100 gallons per day (Essence 5-stage 100 GPD, official product name and specification table)
Filtration stages (maker)	5 stages
NSF/ANSI 58 (maker)	Not listed
Broader named certification	Not listed as a broader named certification on the page we used
Drain ratio (maker)	Not listed
Drain water per product gallon	Not listed
Warranty (maker)	Not listed
Tank capacity (maker)	4 gallons
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Specs source:

APEC: ROES-100

#44

iSpring RCC100P

Best for: 5-stage 100 GPD under-sink RO with a booster pump

0.4/10

What we like

Watch out for

Drain water per product gallon not published by iSpring
Warranty not published by iSpring

Score breakdown

Daily production 24%

NSF/ANSI 58 named 20%

Broader named certification 16%

Drain water per product gallon * 16%

Filtration stages 12%

Warranty * 12%

* Not published by the manufacturer; scored at the lowest published value in this category, so an unpublished figure never outranks a published one.

Daily production	100 GPD
NSF/ANSI 58 named	No
Broader named certification	No
Drain water per product gallon	Not listed
Filtration stages	5
Warranty	Not listed
Daily production (maker)	100 gallons per day (official product name RCC100P / high-capacity boosted 5-stage system)
Filtration stages (maker)	5 stages
NSF/ANSI 58 (maker)	Not listed
Broader named certification	Not listed as a broader named certification on the page we used
Drain ratio (maker)	Not listed
Drain water per product gallon	Not listed
Warranty (maker)	Not listed
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Specs source:

iSpring: RCC100P

#45

APEC ROES-50

Best for: 5-stage 50 GPD under-sink RO with a 4-gallon tank

0.3/10

What we like

Watch out for

Lowest daily production in this comparison (50 GPD)
Drain water per product gallon not published by APEC
Warranty not published by APEC

Score breakdown

Daily production 24%

NSF/ANSI 58 named 20%

Broader named certification 16%

Drain water per product gallon * 16%

Filtration stages 12%

Warranty * 12%

* Not published by the manufacturer; scored at the lowest published value in this category, so an unpublished figure never outranks a published one.

Daily production	50 GPD
NSF/ANSI 58 named	No
Broader named certification	No
Drain water per product gallon	Not listed
Filtration stages	5
Warranty	Not listed
Daily production (maker)	50 gallons per day @ 60 psi, 30 gallons/day @ 50 psi and 77 deg F
Filtration stages (maker)	5 stages
NSF/ANSI 58 (maker)	WQA Certified (standard not named on the page we used)
Broader named certification	Not listed as a broader named certification on the page we used
Drain ratio (maker)	Not listed
Drain water per product gallon	Not listed
Warranty (maker)	Not listed
Tank capacity (maker)	4 gallons
Feed water pressure (maker)	40-85 psi
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Specs source:

APEC: ROES-50

#46

iSpring RCC7P

Best for: 5-stage 75 GPD under-sink RO with a booster pump

0.3/10

What we like

Watch out for

Drain water per product gallon not published by iSpring
Warranty not published by iSpring

Score breakdown

Daily production 24%

NSF/ANSI 58 named 20%

Broader named certification 16%

Drain water per product gallon * 16%

Filtration stages 12%

Warranty * 12%

* Not published by the manufacturer; scored at the lowest published value in this category, so an unpublished figure never outranks a published one.

Daily production	75 GPD
NSF/ANSI 58 named	No
Broader named certification	No
Drain water per product gallon	Not listed
Filtration stages	5
Warranty	Not listed
Daily production (maker)	75 gallons per day
Filtration stages (maker)	5 stages
NSF/ANSI 58 (maker)	Not listed
Broader named certification	Not listed as a broader named certification on the page we used
Drain ratio (maker)	Not listed
Drain water per product gallon	Not listed
Warranty (maker)	Not listed
Pump (maker)	Booster pump (officially a performance-boosted system)
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Specs source:

iSpring: RCC7P

#47

APEC RO-CTOP-C

Best for: Portable 4-stage 90 GPD countertop RO with a carry case

0.2/10

What we like

Watch out for

Drain water per product gallon not published by APEC
Warranty not published by APEC

Score breakdown

Daily production 24%

NSF/ANSI 58 named 20%

Broader named certification 16%

Drain water per product gallon * 16%

Filtration stages 12%

Warranty * 12%

* Not published by the manufacturer; scored at the lowest published value in this category, so an unpublished figure never outranks a published one.

Daily production	90 GPD
NSF/ANSI 58 named	No
Broader named certification	No
Drain water per product gallon	Not listed
Filtration stages	4
Warranty	Not listed
Daily production (maker)	90 gallons per day @ 60 psi, 75 gallons/day @ 50 psi and 77 deg F
Filtration stages (maker)	4 stages
NSF/ANSI 58 (maker)	Not listed
Broader named certification	Not listed as a broader named certification on the page we used
Drain ratio (maker)	Not listed
Drain water per product gallon	Not listed
Warranty (maker)	Not listed
Tank capacity (maker)	tank not included
Package weight (maker)	12 lbs
System dimensions (maker)	16" x 6.5" x 6.5"
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Specs source:

APEC: RO-CTOP-C

#48

APEC RO-CTOP-PH

Best for: Portable 4-stage 90 GPD alkaline countertop RO

0.2/10

What we like

Watch out for

Drain water per product gallon not published by APEC
Warranty not published by APEC

Score breakdown

Daily production 24%

NSF/ANSI 58 named 20%

Broader named certification 16%

Drain water per product gallon * 16%

Filtration stages 12%

Warranty * 12%

* Not published by the manufacturer; scored at the lowest published value in this category, so an unpublished figure never outranks a published one.

Daily production	90 GPD
NSF/ANSI 58 named	No
Broader named certification	No
Drain water per product gallon	Not listed
Filtration stages	4
Warranty	Not listed
Daily production (maker)	90 gallons per day @ 60 psi, 75 gallons/day @ 50 psi and 77 deg F
Filtration stages (maker)	4 stages
NSF/ANSI 58 (maker)	WQA Certified (standard not named on the page we used)
Broader named certification	Not listed as a broader named certification on the page we used
Drain ratio (maker)	Not listed
Drain water per product gallon	Not listed
Warranty (maker)	Not listed
Tank capacity (maker)	tank not included
Alkaline stage (maker)	4th-stage calcite filter
Package weight (maker)	11 lbs
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Specs source:

APEC: RO-CTOP-PH

#49

APEC RO-QUICK90

Best for: Compact 4-stage 90 GPD under-sink RO

0.2/10

What we like

Watch out for

Drain water per product gallon not published by APEC
Warranty not published by APEC

Score breakdown

Daily production 24%

NSF/ANSI 58 named 20%

Broader named certification 16%

Drain water per product gallon * 16%

Filtration stages 12%

Warranty * 12%

* Not published by the manufacturer; scored at the lowest published value in this category, so an unpublished figure never outranks a published one.

Daily production	90 GPD
NSF/ANSI 58 named	No
Broader named certification	No
Drain water per product gallon	Not listed
Filtration stages	4
Warranty	Not listed
Daily production (maker)	90 gallons per day @ 60 psi, 75 gallons/day @ 50 psi and 77 deg F
Filtration stages (maker)	4 stages
NSF/ANSI 58 (maker)	WQA Certified (standard not named on the page we used)
Broader named certification	Not listed as a broader named certification on the page we used
Drain ratio (maker)	Not listed
Drain water per product gallon	Not listed
Warranty (maker)	Not listed
Form factor (maker)	Ultimate compact 4-stage undersink system
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Specs source:

APEC: RO-QUICK90

#50

iSpring RO10001F

Best for: Tankless under-sink RO with a 3:1 pure-to-drain ratio and 0.69 GPM listed flow

0.0/10

What we like

Watch out for

Daily production not published by iSpring
Filtration stages not published by iSpring
Warranty not published by iSpring

Score breakdown

Daily production * 24%

NSF/ANSI 58 named 20%

Broader named certification 16%

Drain water per product gallon 16%

Filtration stages * 12%

Warranty * 12%

* Not published by the manufacturer; scored at the lowest published value in this category, so an unpublished figure never outranks a published one.

Daily production	Not listed
NSF/ANSI 58 named	No
Broader named certification	No
Drain water per product gallon	0.333 gal/gal
Filtration stages	Not listed
Warranty	Not listed
Daily production (maker)	Daily production in gallons per day is not named on the official title or the readable body we used; the page lists 0.69 GPM and 8 oz in 6 seconds instead
Filtration stages (maker)	Not listed
NSF/ANSI 58 (maker)	Not listed
Broader named certification	Not listed as a broader named certification on the page we used
Drain ratio (maker)	3:1 pure-to-drain ratio (official product name)
Drain water per product gallon	0.333 gal/gal (computed)
Warranty (maker)	Not listed
Listed flow (maker)	0.69 GPM; 8 oz in 6 seconds
Filter life (maker)	Up to 2-year life (official product name)
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Specs source:

iSpring: RO10001F

Buying guide: how to choose the right reverse osmosis system

Daily production is a lab rating

Gallons per day is the maker's rated output, usually at a stated pressure and temperature (often 60 psi). Actual flow at a low-pressure municipal tap, or on a well, can be lower. Tankless systems advertise high GPD figures that also depend on a nearby electrical outlet and adequate inlet pressure.

Read the certification line, not the 99% headline

We score NSF/ANSI 58 only when the official page names that standard. A WQA Gold Seal badge or a generic certified claim is quoted, but it is not scored as 58 unless the standard is named. A 58 listing can be TDS-only; broader certified reductions (lead, fluoride, arsenic, or an additional NSF/ANSI 42 or 53 claim) are a separate yes/no criterion.

Drain ratio wording matters

A 2:1 pure-to-drain ratio means two gallons of product water for one gallon of drain water, which we convert to 0.5 gallons of drain water per product gallon and label computed. Traditional tank systems often do not publish a ratio at all; that field is then Not listed and scores at the category minimum. We do not infer a ratio from marketing claims such as saves 800% water.

Installation, wastewater and drinking-water safety

Under-sink and tankless reverse osmosis systems need a drain connection, a minimum inlet pressure, and, on most tankless units, a grounded outlet. Follow the maker's installation manual and local plumbing codes; use a licensed plumber where required. Do not drink the drain (reject) water. These systems are intended for municipally treated or otherwise potable water unless the maker specifically certifies a unit for microbiologically unsafe water. Replace filters and sanitise on the schedule the maker publishes, and shut the system down if you see a leak.

How this ranking is calculated

Score = weighted average of normalised specs, out of 10. Full method

Daily productionThe maker's rated gallons per day, usually at a stated feed pressure. Missing values take the category minimum. Scale: 50 → 1600 GPD.

24%

NSF/ANSI 58 namedYes when the official page names NSF/ANSI 58 (or WQA certification to 58). A generic certified claim without the standard is No.

20%

Broader named certificationYes when the official page names an additional NSF/ANSI standard such as 42 or 53, or lists certified contaminant reductions beyond TDS. NSF/ANSI 372 (lead-free materials) alone is not enough.

16%

Drain water per product gallonComputed from a clearly worded pure-to-drain or product-to-waste ratio. Lower is less wastewater. Missing values, including traditional tank systems that do not publish a ratio, take the category minimum. Scale: 0.33 → 3 gal/gal.

16%

Filtration stagesStage count the maker lists. Missing values take the category minimum. Scale: 3 → 11.

12%

WarrantyLimited warranty length the official page publishes, in years. Missing values take the category minimum. Scale: 1 → 5 yr.

12%

Frequently asked questions

Why isn't a WQA Gold Seal scored as NSF/ANSI 58?

Some official APEC pages say WQA Gold Seal Certified or WQA Certified without naming NSF/ANSI 58 on the page we used. We quote that wording and leave the NSF/ANSI 58 criterion as No unless the standard is actually named. The RO-90 and RO-PH90 pages do publish a certified contaminant-reduction list, which is why their broader-certification criterion is Yes even though 58 is not named.

Why do some tankless models have no stage count?

A few official iSpring tankless titles list GPD and a pure-to-drain ratio but do not publish a stage count in the product name or the readable body we used. We show Not listed and score the missing figure at the category minimum.

Which reverse osmosis systems did you leave out?

We did not include colorways of the same system (for example Waterdrop gold or bronze faucets, or iSpring BLK and GLD finishes) as separate products. Extra-filter bundles such as the APEC ROES-50X and iSpring F3 value packs are omitted because they are the same system plus spare cartridges. We also omitted refurbished listings and combination packages that pair an RO unit with a softener. Official catalogs from GE, Whirlpool, Culligan, Aquasana, Home Master, Frizzlife, SimPure, NU Aqua, AquaTru and RKIN were not turned into complete specification tables in this pass, so those brands are not ranked here.

Did you test these systems or list prices?

No. HydroPick ranks published official specifications only. We do not test units, and we do not show prices or customer ratings.

How is the drain-ratio figure computed?

When a maker lists a 2:1 pure-to-drain ratio, we record 0.5 gallons of drain water per gallon of product water and label that conversion computed. A 3:1 pure-to-drain ratio becomes 0.333 gal/gal. We only do this when the official wording makes the direction clear.

Top pick · 7.5/10Waterdrop X16

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