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How we rank products

Every ranking on this site is calculated, not hand-picked. Here is the whole method.

1. Specs come from the manufacturer

We enter only figures the manufacturer publishes and link the page we used under every product. If a figure isn't published we show "Not listed" instead of guessing.

2. Each spec is scaled from 0 to 1

Each criterion has a fixed reference range, from a "weakest reasonable" value to a "best in class" value (for example 50 to 1,600 gallons per day for reverse osmosis production). A product's figure is placed on that range and clamped between 0 and 1, so scores stay meaningful as products are added. Yes/no features count as 1 or 0. The ranges are listed below.

3. Weights decide what matters most

Each category lists its criteria and weights on the page. The score is the weighted average, multiplied by 10:

score = 10 × Σ(weight × scaled value) ÷ Σ(weight)

4. How missing data is scored

If a spec isn't published (for example drain ratio or warranty), the product scores at the lowest value any product in that category actually published, so an unpublished figure never outranks a published one. The page marks each such cell with an asterisk. Yes/no features that aren't stated count as no. Nothing is ever scored at the category average. NSF or WQA certifications are scored only when the official page names the standard (for example NSF/ANSI 58). A general "certified" claim without a standard is quoted and not scored as a named standard.

5. Prices and ratings switch on automatically

When our retailer feeds supply a current price or customer rating for at least 60% of products in a category, two more criteria join the formula: Price / value (20%) and Customer rating (15%, discounted when there are few reviews). Until then we show "Check price" and never estimate a price.

6. What the score can't tell you

Specs don't capture how a system tastes in your kitchen, how noisy a pump is, or how a softener behaves on your actual hardness and iron levels. Daily production is the maker's rated gallons per day, usually at a stated pressure and temperature, not the flow you will see at a low-pressure tap. Drain-ratio figures are scored only when the maker's wording makes the direction clear (for example "2:1 pure-to-drain"); we convert those to gallons of drain water per gallon of product water and label the conversion computed. Grain capacity and service flow are each maker's own claims. Use the score to shortlist, then read the pros, cons, safety notes and sources. When we add hands-on testing notes, we label them clearly.

7. Money never changes the order

We earn affiliate commissions from some retailers. Commission rates are not an input to the formula, and no brand can pay for placement. See our affiliate disclosure.

Criteria by category

Reverse Osmosis Systems

Water Softeners

Whole-House Water Filters