We checked 96 filters: 44% of reduction claims are brand-tested only
Are water filter claims certified or just tested by the brand?
Of 538 contaminant-reduction claims across 96 current home water filters we track, 299 (about 56%) are listed by a certifier (NSF, WQA, IAPMO or CSA) and 239 (44%) rest only on a brand-paid lab test that no certifier lists.
We counted every reduction claim for the 18 contaminants we track, across 96 current filters, using data checked on 2026-10-23.
299 claims (about 56%) are certified: the exact model and the claim appear in a public certifier listing from NSF, WQA, IAPMO R&T or CSA, which also audit the factory.
239 claims (44%) are 'tested only': the brand cites a lab test, sometimes run to NSF/ANSI methods, but no certifier lists the claim or rechecks it.
58 of the 96 current filters have at least one tested-only claim. Examples include the Clearly Filtered pitcher, whose lead, PFOA/PFOS and fluoride figures come from a lab report published by the brand, and the Frizzlife PD600, whose RO claims come from an SGS test cited by the brand.
A tested-only claim is not necessarily wrong, but it cannot be checked in a certifier database. Each filter page on our site marks every claim as certified or tested only.
Filters in this update
