Editorial policy

What we use as evidence

In order of preference: the current manufacturer document for the exact model (performance data sheet, manual, product page); a certification body's public listing; guidance from public agencies such as the EPA, CDC and state health departments; and independent standards bodies such as NSF. Every factual claim about a product links to a source, and each guide ends with its full source list and the date each one was accessed.

Hands-on testing

We have not tested the products in our current guides. The guides are labeled research-based, and we don't write as though we have used a product. Phrases like "we tested" or "in our experience" will only ever appear with a described test behind them. We have also not conducted any laboratory water testing.

AI drafting and human review

Guides on this site may be drafted by an AI model working from the listed sources. The model is not a person and isn't credited as one. Each guide states who drafted it, when its claims were checked against sources, and whether the publisher has personally reviewed it. A guide is only credited to a person when that person actually wrote or reviewed it, and that review is recorded with a date.

How we handle product claims

• A certification applies to specific models and specific claims. We don't extend one model's certification to other products from the same brand.
• Reduction figures are reported as the manufacturer's data sheet states them, with the standard and test conditions.
• A manufacturer's claim is presented as its claim. Where documents conflict, we say so instead of quietly choosing the better number.
• If a fact isn't published, we say it isn't published. We don't estimate it and present the estimate as fact.

Water and health

We explain what standards and data sheets say. We don't judge whether your water is safe, predict health effects, or offer treatment advice. A home filter isn't a substitute for testing, for your utility's reports, or for medical advice. A TDS reading isn't a measure of safety, filtering isn't softening, and reverse osmosis doesn't remove everything.

Prices and costs

Prices come from the merchant's own page and carry the date we checked them. After 30 days without a new check, a price is removed from the site automatically rather than left looking current. Our cost tables show their assumptions, and estimates are labeled as estimates.

Money and independence

Commission rates are not an input to any comparison. Nothing in the product data that drives our tables records what a merchant pays. Merchants don't review or approve our guides before publication. See the affiliate disclosure.

Images

Photographs on this site are AI-generated illustrations of generic objects and settings. They aren't pictures of a named product and they aren't evidence of testing.

Updates and corrections

Each guide shows its publication date and, when its content has substantively changed, an updated date. We don't change a date just to make a page look fresh. If we find an error we correct the page, and we note corrections that change a guide's substance.