ZeroWater vs Clearly Filtered: which is actually certified — and what does a certified gallon cost?

Last reviewed July 2026.

Same job, same shelf — but the certifications underneath are not the same. Here is ZeroWater against Clearly Filtered on the only two axes we score: what the certification actually covers, and what a certified gallon costs.

• ZeroWater: cheapest certified-for-lead filter is the ZR-002 at $1.233/certified gallon (lead claim: IAPMO R&T, NSF/ANSI 53).
• Clearly Filtered: certified to NSF/ANSI 42 only — genuinely certified, but no certified lead claim.

Every model, side by side

Price per filter ÷ certified capacity in gallons. Certification data from the certifiers' public listings; the listing always wins.

How often you actually replace them

Cost per gallon is the fair comparison, but it hides the part you live with. The Clearly Filtered CF-Pitcher is certified for 100 gallons; the ZeroWater ZR-002 for 15 — so you buy and fit the second one about 6.7× as often for the same volume of water. At roughly half a gallon of drinking water per person per day, that is the difference between a filter you think about twice a year and one you think about every few weeks.

It matters beyond convenience: the certified claim only holds within the rated capacity. A filter run long past its gallons still passes water and still looks fine, but nothing about the lead or PFOA/PFOS claim applies any more. The brand with the shorter interval is the one more likely to be used out of spec.

So which one

For a certified lead claim this one is not close: ZeroWater. The ZR-002 carries a certified lead claim (IAPMO R&T, NSF/ANSI 53) and works out at $1.233 per certified gallon. It is the only side of this comparison where a lead claim is both listed and priceable.

Clearly Filtered is genuinely certified, but to NSF/ANSI 42 — taste, odour and chlorine. That is a real listing for a real claim, and it is not a lead claim. No amount of 42 adds up to 53; they are tested against different contaminants. If lead is why you are filtering, 42-only is a miss however reputable the brand.

None of which makes Clearly Filtered a bad filter at what it is certified to do — it makes it the wrong filter to buy for lead. If lead is not your concern, the comparison above is the wrong one to be reading; start from the full ranking and pick on the claim you actually want.

The full stories: Is ZeroWater NSF certified? · Is Clearly Filtered NSF certified? · what 42, 53 and 401 mean

We do not test filters — we index what accredited certifiers publish, with attribution, and make no health or treatment claims. A certification covers a specific model against a specific standard; it is not a general seal of quality. We are not affiliated with NSF International.

Some product links on this page are affiliate links: as an Amazon Associate we earn from qualifying purchases, at no extra cost to you. Affiliate status never changes a ranking or a verdict — full affiliate disclosure.