Contaminant · Water
Mercury
EPA MCL 0.002 mg/L (2 ppb). 9 of the water filters we score hold an accredited NSF, WQA, or IAPMO certification to reduce Mercury, and 6 more market it with no accredited certification we could verify. A claim is not a certification.
What it is
Mercury is a naturally occurring heavy metal that can dissolve into groundwater and surface water. It enters drinking water from natural mineral deposits, discharge from refineries and factories, and runoff from landfills and croplands. Because it carries no taste, color, or smell, mercury in tap water is detected only by laboratory testing.
Why it matters
The EPA sets a federal maximum contaminant level (MCL) for mercury of 0.002 mg/L, which is 2 parts per billion, in public drinking water. That number is a regulatory reference point for the amount allowed in treated water, not a line that describes any individual filter's performance. We score whether a filter is certified to reduce mercury, not any health outcome.
What removes it
Mercury reduction is certified two ways: under NSF/ANSI 58 for reverse osmosis systems, and under NSF/ANSI 53 for select activated-carbon filters whose media is specifically formulated to bind mercury. The trap is that ordinary carbon filtration certified only under NSF/ANSI 42 targets taste and odor and is not certified for mercury. So a pitcher or cartridge earns credit here only when it carries an NSF/ANSI 53 or 58 certification that names mercury specifically, not a general carbon claim.
Reference: EPA National Primary Drinking Water Regulations, mercury MCL 0.002 mg/L; NSF/ANSI 53 (drinking water treatment units, health effects) and NSF/ANSI 58 (reverse osmosis).
Scored filters certified for Mercury
- 8.4Brita Elite Pitcher (10-Cup)
A pour-through pitcher whose Elite filter is certified to reduce lead, mercury, cadmium and more, with a long 120-gallon cartridge.
- 7.5Culligan US-EZ-4 Under-Sink
An under-sink filter genuinely IAPMO certified to NSF/ANSI 42, 53 and 401 for lead, cysts, VOCs, mercury and PFOA/PFOS.
- 7.2Aquasana AQ-5200 Under-Sink
Certified for lead and PFAS, cheap per gallon, marketing matches the certified scope.
- 6.6Waterdrop G3P800 Tankless RO
A tankless 800 GPD reverse-osmosis system IAPMO-certified to NSF/ANSI 42, 53, 58 and 372 for a broad contaminant list including lead, PFAS, arsenic, nitrate and fluoride.
- 6.4PUR Plus Faucet Mount (PFM400H)
A faucet-mount system whose RF-9999 cartridge is genuinely NSF certified for lead, chlorine, mercury and microplastic reduction.
- 5.9PUR Plus Pitcher (7-Cup)
An affordable pitcher certified to reduce lead, mercury, microplastics and chlorine, though its 40-gallon filter needs frequent swaps.
- 5.6Brita Standard Pitcher
An everyday ion-exchange pitcher certified for chlorine, copper, cadmium and mercury - but notably NOT certified for lead.
- 4.9ZeroWater 5-Stage Pitcher (7-Cup)
A five-stage ion-exchange pitcher certified for lead, chromium-6 and PFOA/PFOS - but a short 15-gallon filter makes it costly to run.
- 4.1Epic Smart Shield Under-Sink
A slim inline under-sink filter genuinely certified by IAPMO to NSF/ANSI 42, 53 and 401 for lead, VOCs and more - though its PFAS reduction is tested to standards, not in the certified scope.
Marketed for Mercury, but not certified
These scored filters market Mercury reduction but we found no accredited NSF, WQA, or IAPMO certification for it - "tested to" is not "certified to." Absence of certification is not proof a product fails to reduce it, only that we found no independent verification.
- 6.8Frizzlife SK99 Under-Sink Filter
A direct-connect 3-stage under-sink filter with a 0.5 micron carbon block, IAPMO certified to NSF/ANSI 42 and 53 for chlorine, lead, VOCs and particulate. Its broader claims (chloramine, PFAS, fluoride) are marketed but not certified.
- 4.9Express Water RO5DX 5-Stage RO
A 5-stage under-sink RO whose contaminant figures come from third-party lab testing (QFT Laboratory) to NSF/ANSI methods; we found no accredited NSF, WQA or IAPMO certification listing for this model.
- 2.7LifeStraw Home Pitcher
A membrane-and-carbon pitcher marketed against bacteria, microplastics, lead and PFAS, but its claims rest on 'tested to' lab data rather than active third-party certification.
- 2.5Clearly Filtered Pitcher
Certified only to NSF/ANSI 42 and 372, its 365+ contaminant claims come from non-accredited lab testing, not health-effects certification.
- 1.7Clearly Filtered 3-Stage Under-Sink
A three-stage under-sink system the brand says targets 232+ contaminants, but its performance is lab-tested to NSF protocols rather than third-party certified.
- 1.5Great Value Water Filter Pitcher (HS528N)
A budget store-brand pitcher whose Walmart listing says 'Certified to NSF/ANSI 42&53' but names no certifier, number, or registry - an unverifiable claim that earns no certified credit here. No standalone filter price is published, so cost per gallon also can't be computed.
FAQ
- Does a Brita or carbon pitcher remove mercury?
- Only if that specific pitcher is certified for mercury under NSF/ANSI 53. Several carbon pitchers in our catalog, including the Brita Elite, Brita Standard, PUR Plus, and ZeroWater pitchers, do carry an NSF/ANSI 53 mercury certification, so they earn credit in our scoring. A plain carbon pitcher certified only under NSF/ANSI 42 for taste and odor does not, and you should not assume mercury reduction from a general carbon claim. Check the model's certification listing for mercury by name.
- Does boiling water remove mercury?
- No. Boiling does not remove dissolved mercury and can concentrate it as water evaporates. Reducing mercury relies on certified treatment such as reverse osmosis under NSF/ANSI 58 or an activated-carbon filter certified for mercury under NSF/ANSI 53.
Related
- Best Water Filter for Mercury, ranked and scored
- Is your water filter NSF certified? The verified list
- How to check a filter's certification yourself
- Lead in drinking water
- PFAS (PFOA / PFOS) in drinking water
- Chlorine and Chloramine in drinking water
- Volatile Organic Compounds (VOCs) in drinking water
- Nitrate in drinking water
- Arsenic in drinking water
- Hard Water (Hardness) in drinking water
- Fluoride in drinking water
- Chromium-6 (Hexavalent Chromium) in drinking water
- Microplastics in drinking water
- Cysts (Cryptosporidium and Giardia) in drinking water
- Pharmaceuticals and Emerging Compounds in drinking water
- Asbestos in drinking water
- Copper in drinking water