- Home
- Testing methodology
Testing methodology
Every recommendation on WaterCriteria follows the same process, so you can compare pages with confidence.
Certified claims only
A contaminant counts as removed only when an independent certification listing says so for that exact model.
A clear verdict
Each guide says who the system suits, who should look elsewhere, and what to check before you buy.
No paid placements
Brands cannot buy a review or a spot on a list. Partner codes save you money; they never decide what we recommend.
Kept current
Prices are dated, codes are updated across the site at once, and pages are revised when a product, standard or rule changes.
Where our facts come from
We read each product's performance data sheet and check its claims against the NSF, IAPMO, WQA or CSA certification listings, which name the exact contaminants and standards a model is certified for. We use EPA drinking-water standards and state well-testing guidance for context.
What we check, by product type
| Certification | NSF/ANSI 42, 53, 58, 401, P473 or 55 listings for the exact model, and which contaminants each listing covers. |
|---|---|
| Capacity and flow | Rated gallons per cartridge, gallons per day for RO, flow rate in gallons per minute for whole-house systems. |
| Cost to own | Cartridge and membrane prices, replacement intervals, wastewater ratio and three-year running cost. |
| Installation | Plumbing connections, space under the sink or at the main line, drain and power needs. |
| Softeners and well systems | Grain capacity, regeneration method, salt use, iron and manganese limits, UV dose and flow rating. |
Hands-on testing versus research
A review carries a "Hands-on tested" badge only when our team has used the product, and it lists the date and what we did. Every other page is built from published specs, governing-body rules, the brand's own documentation and owner feedback, and says so. Comparisons are research-based unless marked otherwise.
Prices and codes
Prices come from each brand's own store and are dated on every review. Reader codes come directly from the brands we partner with. When a brand changes an offer, we update the code everywhere it appears on the site at once.
Corrections
If you spot something out of date, email [email protected] and we'll check it and fix it.