One claim, counted properly

Each roster is a single NSF claim search, fetched, parsed into distinct models and checked against NSF’s own reported total before publication.

That last step is not decorative. A parser that silently returned zero rows against a reported 145 was caught by exactly this check, and the counts on this site are only trustworthy because it runs every time.

Counts are distinct model designations, deduplicated by company and model. NSF lists a model once per facility and per claim, so its row totals run higher — lead returns 1,003 rows and resolves to 615 models.

What the counts actually tell you

The spread is two orders of magnitude

Certified fields are not comparable in size, and the difference decides whether you have a choice or a single option. Cyst reduction covers 1,104 distinct models and microplastics 806, while nitrate has 84, microcystin 48, radon 30 from two companies and Filter First 28 from one.

A large field moves the decision to cartridge cost and form factor. A small one means the claim itself is the constraint, which is better discovered before comparing products than after.

Some claims exist in exactly one shape

Where a claim follows a technology rather than a material, the product form comes with it. Every model certified for fluoride, nitrate or hexavalent chromium is plumbed in to a separate tap, because all three are NSF/ANSI 58 claims and reverse osmosis is installed under a sink. No pitcher, faucet mount, refrigerator filter or point-of-entry unit holds any of them, so for those three contaminants the shape of the answer is fixed before shopping starts.

Whole-house is nearly empty of health claims

Across every roster here, point-of-entry products hold four trihalomethane claims, the same four for VOC, and 114 softeners certified for radium and barium. Lead, PFAS, cyst, fluoride, nitrate, hexavalent chromium, arsenic, turbidity and microplastics return none at all. Chlorine and taste-and-odour claims under NSF/ANSI 42 are the exception, which is why whole-house systems are useful for aesthetics and largely unavailable for health claims.

Choose which roster to open

Open a roster if you have a contaminant and want to know whether a certified option exists, and in what form.

Skip the rosters if you have not yet established a number. A count of certified models answers nothing without something to treat.

Stop entirely if the roster shows no certified product in a form you can fit. That is a complete answer, and it is cheaper than the alternative.

The rosters

Claim Certified models Notable
Lead 615 Six product forms; 282 are fridge filters
Cyst 1,104 The largest field on the site
PFAS 72 PFOA and PFOS only; no GenX claim exists
Trihalomethanes 153 Includes four point-of-entry models
VOC 146 One claim covering 53 named contaminants
Nitrate 84 One product form only
Fluoride 127 One product form only
Arsenic 135 Every claim is pentavalent-only
Chloramine 137 Separate claim from chlorine
Whole house Few Almost no health claims certified
Shower filters 6 One claim, aesthetic effects only

Bottled water is the other comparison

Not a certified product in this sense, and regulated by FDA rather than EPA.

→ Bottled water versus tap: who regulates what

Before opening any of them

→ What is in city water: the regulated, the advisory, and the unmeasured → How to check a certification claim yourself → Which claims exist in which product form → The regulated contaminants with no certified filter