How We Research Water Treatment Systems

Last updated September 28, 2026

Every article on House Water Guide follows the same process, so readers know what it is — and is not — based on.

1. Sources

  • Manufacturer documentation: installation and owner's manuals, specification sheets, published flow rates, cartridge schedules and warranty terms.
  • Independent certification listings: where a system claims a NSF/ANSI standard, we look for the listing rather than repeating the claim. A standard number printed on a box is not the same as a certified listing, and we say which one we found.
  • Plumbing code language: where a requirement comes from code rather than from a manufacturer, we describe what the model code text says and note that local amendments override it.
  • Public user feedback: read for recurring patterns — the same failure at the same point — rather than individual anecdotes.

Unless an article states otherwise, it is not based on first-hand installation or testing. We do not describe work we did not do.

2. Certification claims

"Tested to NSF/ANSI 53" and "certified to NSF/ANSI 53" are different statements, and the difference matters for anyone buying a system to remove a specific contaminant. Where we can only confirm the weaker claim, the article says so, and where a certification covers only some of a system's stages, we say which.

3. Pricing

Equipment prices, bundles and cartridge costs change often, and the cartridge cost usually matters more over five years than the price of the housing. Articles show prices as starting points or ranges and link to the manufacturer. Always confirm current pricing before buying.

4. No scores, no badges

We do not assign scores, star ratings or "best overall" badges. Each article lists strengths, limitations and the kind of household the system fits, and each category page explains how to choose between approaches.

5. Updates and corrections

Each page shows the date it was last updated. When a manufacturer changes a specification or a reader reports an error, we update the page and its date. Send corrections through the contact page.

6. Affiliate links

Affiliate relationships never decide what we cover or what we say about a system. Affiliate links are marked for search engines with rel="sponsored", and equipment from manufacturers without an affiliate program is covered the same way. See the affiliate disclosure.