Direct answer: Water System Guide builds every public page from a documented evidence layer: each fact carries a source class, source, observation date and review date, and unknown states are marked unknown. Recommendations are conditional — they depend on water source, test evidence, exact certified claims, household demand and installation constraints — and are never presented as universal winners.
Evidence classes
- Measured facts — utility reports, certified product listings, manufacturer documentation, and primary-source data, each with an observation date and review date.
- Derived recommendations — guidance built from measured facts plus explicit assumptions; always labeled as conditional.
- Unknown states — where evidence is absent or unverified, the page says so rather than estimating.
Source standards
- Public water and health facts cite the relevant utility, public water system, or agency (for example CDC, EPA, NSF) directly.
- Product-family scope comes from manufacturer documentation; it never proves availability, dealer status, or fit for a specific property.
- Certification claims are tied to the exact model’s current listing, not a brand badge.
- No invented addresses, licenses, certifications, awards, reviews, prices, or firsthand claims.
Review and correction
- Pages carry effective and review dates.
- Material corrections are made without silently rewriting history; version changes are noted.
- Errors reported through the contact path are investigated and corrected with the change recorded.
How evidence appears on a published page
Important conclusions are written in plain text before supporting tables so they can be read, quoted and checked without interpreting a visual alone. Substantial research pages publish the responsible editorial organization, the last verification date, a methodology link and a source record. When a product claim depends on a certifier listing or document revision, the page names that evidence relationship in the text instead of relying on a brand badge.
A published evidence statement should make the relationship clear, for example:
- Manufacturer documentation reviewed — the named manual, specification, catalog or warranty establishes the product-family or model claim described on the page.
- Certification record reviewed — the exact model, standard, named claim and rated conditions are checked against the certifier record; a logo alone is not treated as proof.
- Water evidence reviewed — a utility report, public-water-system record, agency source or fit-for-purpose test establishes the water fact being applied.
- Unknown retained — availability, ownership, dealer status, price, inventory or another changing fact remains unstated when current primary evidence does not establish it.
Authorship and editorial accountability
Water System Guide is the named research and publishing organization. Pages identify Water System Guide editorial as responsible for research and writing and link to this methodology for the evidence-review process. A technical or professional reviewer is named only when that person has actually reviewed the page and their relevant background can be documented; no reviewer identity is inferred or invented.
What this means for recommendations
No page on Water System Guide picks a universal best. Every recommendation is a match between the water source, household goal, plumbing conditions, and verified equipment capability — and the page shows the evidence and assumptions that led to it.
For the next focused decision, use the NSF-certified water filter verification guide.