Home water filters, what they remove and the trade-offs

Home water filters differ in what they remove. Activated carbon filters certified for lead reduced lead in tap water to very low levels in a large field study, but remove almost no calcium or magnesium; reverse osmosis removes most dissolved metals, including those minerals, and both carbon and reverse osmosis units can greatly reduce PFAS when maintained, though real-world performance varies and short-chain PFAS are harder to remove. Boiling hard tap water removed most added micro- and nanoplastics in a laboratory study, and bacteria persisted in filter jugs used carelessly. Independent certification of the specific contaminant claim, and replacing cartridges on schedule, are the practical guides; most of this evidence comes from laboratory and field measurements rather than health-outcome trials.

Evidence retrieved up to 17 October 2026

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5 research claims

What the research shows

In homes supplied with lead-contaminated tap water, faucet-mounted activated carbon block filters certified for lead and fine-particle reduction lowered lead in filtered water to very low levels in almost all samples.

No known concerns at usual amountsBenefit

Who this is about

households with lead in their tap water

Details and sources

Practical note

Graded moderate: a direct field measurement at over 345 homes with a large, consistent reduction (over 97% of filtered samples below 0.5 micrograms per litre), matching the certification test the filters had passed; not higher because it is a single observational field study in one city's water.

Safety note

The field study stressed proper installation and maintenance; a filter used past its rated capacity may no longer perform as certified.

Sources

Supports“Over 97% of filtered water samples contained lead below 0.5 µg/L.” (Abstract) Bosscher V, Lytle DA, Schock MR, Porter A, Del Toral M. 2019. Journal of Environmental Science and Health, Part A. POU water filters effectively reduce lead in drinking water: a demonstration field study in flint, Michigan. publisher copyright; metadata and short quotes only; Courtesy of the U.S. National Library of Medicine
Context“These certifications verify the effectiveness of the filters and accuracy of the contaminant reduction claims.” (Why is certification recommended?) US Environmental Protection Agency. US EPA. Identifying Drinking Water Filters Certified to Reduce PFAS. US government work, public domain; credit US EPA

Point-of-use activated carbon, ion-exchange and reverse osmosis systems can greatly reduce PFAS in tap water, but real-world performance is less well characterised, short-chain PFAS are removed less reliably, and poorly maintained carbon filters may even raise PFAS levels.

No known concerns at usual amountsBenefit

Who this is about

households with PFAS in their tap water

Details and sources

Practical note

Graded low: laboratory and certification testing are consistent, but the 2024 review found only five peer-reviewed studies of removal in real-life use, with inconsistent test methods. US EPA guidance points to products certified under NSF/ANSI 53 or, for reverse osmosis, NSF/ANSI 58 for PFAS reduction.

Safety note

US EPA notes that certification standards as of April 2024 did not yet show removal down to its new drinking water limits for PFAS.

Sources

Supports“Furthermore, improperly maintained activated carbon systems might even raise PFAS levels in purified water.” (Abstract) MacKeown H, Magi E, Di Carro M, Benedetti B. 2024. Science of the Total Environment. Removal of perfluoroalkyl and polyfluoroalkyl substances from tap water by means of point-of-use treatment: A review. publisher copyright; metadata and short quotes only; Courtesy of the U.S. National Library of Medicine
Supports“EPA found that the GAC, IX, and RO point-of-use systems studied can greatly reduce PFAS levels.” (Filter types) US Environmental Protection Agency. US EPA. Identifying Drinking Water Filters Certified to Reduce PFAS. US government work, public domain; credit US EPA
Context“Limited to the findings described, not all filters were demonstrated to be effective, especially against short-chain PFAS.” (Abstract) MacKeown H, Magi E, Di Carro M, Benedetti B. 2024. Science of the Total Environment. Removal of perfluoroalkyl and polyfluoroalkyl substances from tap water by means of point-of-use treatment: A review. publisher copyright; metadata and short quotes only; Courtesy of the U.S. National Library of Medicine

Reverse osmosis systems remove most dissolved metals from tap water, including calcium, while activated carbon filters remove almost none of the calcium and magnesium; in a study of children, drinking water type was associated with serum calcium and magnesium levels.

No known concerns at usual amountsUnclear

Who this is about

people drinking reverse osmosis or carbon-filtered tap water

Details and sources

Practical note

Graded low: the removal figures come from one laboratory study of point-of-use systems (calcium, manganese, iron and copper each removed above 98% by reverse osmosis; calcium and magnesium below 1% by carbon), and the link to blood levels from one comparative study of children aged 9-13.

Vegan note

For people on a plant-based diet who get part of their calcium and magnesium from mineral-rich water, reverse osmosis removes that contribution.

Safety note

Whether removing minerals from drinking water matters depends on how much calcium and magnesium the diet supplies; evidence on outcomes is limited and observational.

Sources

Supports“Calcium (Ca) and magnesium (Mg) were poorly removed by AC systems, with efficiencies of less than 1%.” (Abstract) Yu HY, Gupta S, Zhou Z. 2024. Chemosphere. Removal of metals and assimilable organic carbon by activated carbon and reverse osmosis point-of-use water filtration systems. publisher copyright; metadata and short quotes only; Courtesy of the U.S. National Library of Medicine
Supports“Drinking water type impacts serum calcium, magnesium, phosphate, and alkaline phosphatase levels in children.” (Abstract) Thippeswamy HM, Shanbhog R, Kumar MN, Prashanth SN, Smitha P. 2025. Scientific Reports. Comparison of serum calcium, magnesium, phosphate, alkaline phosphatase, and vitamin D levels in children consuming reverse osmosis, non reverse osmosis, and high fluoride drinking water. publisher copyright; metadata and short quotes only; Courtesy of the U.S. National Library of Medicine
Context“Mn and U removal in RO systems exceeded 95%, while Ca, Mn, Fe, and Cu were all removed with efficiencies greater than 98%.” (Abstract) Yu HY, Gupta S, Zhou Z. 2024. Chemosphere. Removal of metals and assimilable organic carbon by activated carbon and reverse osmosis point-of-use water filtration systems. publisher copyright; metadata and short quotes only; Courtesy of the U.S. National Library of Medicine

In laboratory tests, boiling hard tap water removed at least 80% of added polystyrene, polyethylene and polypropylene micro- and nanoplastics, which co-precipitated with the calcium carbonate scale that forms on boiling.

No known concerns at usual amountsBenefit

Who this is about

households using hard tap water

Details and sources

Practical note

Graded very low: a single laboratory study with plastic particles added to tap water, so indirect for the particles people actually drink and without health outcomes.

Safety note

The scale that carries the particles has to be separated afterwards, for example by filtering the cooled water.

Sources

Supports“Boiling hard water (>120 mg L–1 of CaCO3) can remove at least 80% of polystyrene, polyethylene, and polypropylene NMPs size between 0.1 and 150 μm.” (Abstract) Yu Z, Wang J, Liu L, Li Z, Zeng E. 2024. Environmental Science & Technology Letters. Drinking Boiled Tap Water Reduces Human Intake of Nanoplastics and Microplastics. publisher copyright; metadata and short quotes only

In a laboratory simulation of careless use, bacteria persisted in the filtered water of all filter jugs tested over the cartridge lifetime, and household filters work as intended only when cartridges are maintained and replaced on schedule.

Take care: see the safety noteRisk

Who this is about

households using filter jugs and point-of-use filters

Safety note

Filtered water left standing in a jug can carry high bacterial counts; the studies point to the manufacturer's cleaning and cartridge-replacement intervals.

Details and sources

Practical note

Graded low: one laboratory simulation of nine jugs with bacteria added to the water, consistent with US EPA guidance that filters are effective only when maintained.

Sources

Supports“P. aeruginosa confirmed its persistence over time in all the jugs and its ability to potentially colonize surfaces and cartridges.” (Abstract) Briancesco R, Paduano S, Semproni M, Vitanza L, Bonadonna L. 2020. International Journal of Environmental Research and Public Health. Behavior of Pseudomonas aeruginosa and Enterobacter aerogenes in Water from Filter Jugs. CC BY; credit Briancesco et al., IJERPH 2020
Supports“Filters are only effective if they are maintained according to the manufacturer’s instructions for how long their filters or membranes will last before they need to be replaced.” (Filter types) US Environmental Protection Agency. US EPA. Identifying Drinking Water Filters Certified to Reduce PFAS. US government work, public domain; credit US EPA

What the research shows

In homes supplied with lead-contaminated tap water, faucet-mounted activated carbon block filters certified for lead and fine-particle reduction lowered lead in filtered water to very low levels in almost all samples.

Who this is about

Practical note

Safety note

Sources

Point-of-use activated carbon, ion-exchange and reverse osmosis systems can greatly reduce PFAS in tap water, but real-world performance is less well characterised, short-chain PFAS are removed less reliably, and poorly maintained carbon filters may even raise PFAS levels.

Who this is about

Practical note

Safety note

Sources

Reverse osmosis systems remove most dissolved metals from tap water, including calcium, while activated carbon filters remove almost none of the calcium and magnesium; in a study of children, drinking water type was associated with serum calcium and magnesium levels.

Who this is about

Practical note

Vegan note

Safety note

Sources

In laboratory tests, boiling hard tap water removed at least 80% of added polystyrene, polyethylene and polypropylene micro- and nanoplastics, which co-precipitated with the calcium carbonate scale that forms on boiling.

Who this is about

Practical note

Safety note

Sources

In a laboratory simulation of careless use, bacteria persisted in the filtered water of all filter jugs tested over the cartridge lifetime, and household filters work as intended only when cartridges are maintained and replaced on schedule.

Who this is about

Safety note

Practical note

Sources

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