Methodology — how Water Filter Finder makes its recommendations

How we make recommendations

This page exists so you can decide whether to trust the rest of the site. Skim it once; come back if a specific claim looks wrong.

What this site is

Water Filter Finder is an editorial guide to home water filtration. We help readers (1) understand what's in their tap water, (2) figure out which filter type fits their home and budget, and (3) compare specific certified systems before buying.

What this site is not

We do not test products in a home lab. We do not hold any laboratory accreditation. No one on the Water Filter Finder editorial team claims to have personally measured a filter's contaminant reduction.

When we say a specific product carries a specific NSF/ANSI certification claim, that statement is sourced from a third-party certification database — not from us. The database link is included with the claim every time.

Where our data comes from

Every cert claim on this site is anchored to one of these public databases:

• NSF Drinking Water Treatment Units listings — search at info.nsf.org/Certified/dwtu. The most rigorous US database; daily-refreshed.
• WQA Gold Seal product listings — search at find.wqa.org/find-products. Complementary to NSF DWTU; many brands listed here are not in NSF DWTU and vice versa.
• EWG Tap Water Database — search by zip at ewg.org/tapwater. Per-utility contaminant data sourced from public Consumer Confidence Reports.
• EPA ECHO — utility-level compliance and enforcement records at echo.epa.gov.

For any product cert claim where the brand is not listed in NSF DWTU or WQA Gold Seal, we either cite an IAPMO listing or write a "tested to NSF/ANSI X, not listed in NSF DWTU or WQA Gold Seal as of [date]" caveat. We do not silently accept manufacturer-only claims as certified.

How we pick products

When a page recommends specific products, the selection rule is:

1. Cert presence in NSF DWTU or WQA Gold Seal (or, with a caveat, IAPMO) for the specific contaminant claim being made.
2. Price tier match to the article intent. A page about "best under-sink RO" doesn't include $1,500 whole-house systems; a page about "whole-house" doesn't include pitcher filters.
3. Availability through a real retail channel — either an affiliate program (Aquasana, APEC, Waterdrop, iSpring) or general Amazon retail. We do not recommend products we can't actually link readers to.
4. Editorial fit — does this product genuinely solve the problem the page is about? We exclude products that technically fit category gates but aren't a good answer to the question.

We do not rank products by which one pays the highest affiliate commission. This is not because we're virtuous — it's because the rates across our partners cluster within a narrow band, and the long-term cost of a misleading recommendation (reader doesn't come back) is much higher than the short-term commission delta on a single sale.

How we make money

Read /affiliate-disclosure for the legal version. The short version:

When you click a "Buy on Amazon" or "Buy from Aquasana" link and purchase, Water Filter Finder earns a commission. The commission does not change your price. We do not accept payment for editorial placement; recommendations are independent of which brand pays more.

We do not disclose specific commission rates from individual programs — this is standard publisher discipline for programs managed through networks like Impact.com that ask publishers not to publish rate-level economics. Our recommendations would not change if rates were rebalanced; that's the test.

What we don't claim

We avoid the following kinds of claims throughout the site:

• "Your water is unsafe" — we describe what your Consumer Confidence Report says, including contaminants detected above EPA guidelines, but we do not make safety determinations on your behalf. Talk to your utility, your state department of health, or your doctor for medical guidance.
• "Filter X removes 100% of [contaminant]" — we cite specific NSF/ANSI standards and the percentage reductions documented in those standards. No filter removes 100% of anything; that's not how filtration testing works.
• "FDA-approved" / "EPA-certified water filter" — neither agency certifies consumer water filters. NSF (a third-party certifier) and state-level certification programs do.
• Made-up first-person experience — no one on the editorial team is presented with a fabricated regulatory-agency background, certification-body audit history, or in-house laboratory testing role. If you see a byline like "Water Filter Finder editorial team," that's accurate. There is no fictional named lead reviewer.

How to challenge a claim

If a cite link is broken, a cert claim looks wrong, or a price hasn't been updated in a long time, email us at contact@waterfilterfinder.com. We aim to respond within a week, fix verified issues within two weeks, and publish a correction with a date stamp on the affected page.

If a manufacturer disputes a claim about their product, the same process applies. We will not remove the disputed claim before review, but we will add the manufacturer's position alongside ours pending verification.

Version

This methodology was published on the Water Filter Finder launch date and is versioned at v1.0. Material updates are dated on this page.