Product intelligence · by concern
Water Filters by Concern
Start with the water problem, not the product. Each concern shows what filters can and cannot do, the certification to check, and the models PurityMap has analysed.
Choose a concern
What filters can and cannot do
PFAS
14 productsPer- and polyfluoroalkyl "forever chemicals" such as PFOA and PFOS.9 of 14 with current certification evidence for PFASTreatsFilters certified for PFAS reduction lower PFOA, PFOS and related compounds in drinking water.Does not solveThey do not address unrelated problems such as hardness scale, sediment, or microbial risk unless separately certified for them.Certification to checkNSF/ANSI 53Look for NSF/ANSI 53 or 58 naming the compound; RO systems often carry it under 53.PFAS: products and evidence →Lead
15 productsLead that can enter tap water from service lines and household plumbing.13 of 15 with current certification evidence for LeadTreatsFilters certified for lead reduction lower dissolved and particulate lead at the treated tap.Does not solveA point-of-use filter treats one faucet. It does not replace a lead service line or home plumbing, and does not address PFAS or hardness unless separately certified.Certification to checkNSF/ANSI 53Look for NSF/ANSI 53 with a lead reduction claim (tested at pH 6.5 and 8.5).Lead: products and evidence →Hard water
2 productsCalcium and magnesium that cause scale, spotting, and soap problems.2 of 2 with current certification evidence for Hard waterTreatsWater softeners (ion exchange) and conditioners reduce or alter hardness minerals to limit scale.Does not solveHardness is an aesthetic and appliance issue, not a health contaminant; softeners do not remove lead, PFAS, or microbes.Certification to checkNSF/ANSI 44Cation-exchange softeners are covered by NSF/ANSI 44; performance is described by capacity and grains rather than a contaminant-reduction claim.Hard water: products and evidence →Chlorine & disinfection by-products
15 productsChlorine taste and odor, and disinfection by-products such as trihalomethanes.None of 15 verified for Chlorine & disinfection by-products yetTreatsActivated-carbon filters reduce chlorine taste and odor; some are also certified for specific disinfection by-products.Does not solveA taste-and-odor carbon filter is not the same as a certified by-product or lead filter, and does not soften water or remove PFAS unless separately certified.Certification to checkNSF/ANSI 42NSF/ANSI 53Chlorine taste and odor is NSF/ANSI 42; specific by-product reduction (e.g. TTHM) is NSF/ANSI 53.Chlorine & disinfection by-products: products and evidence →Nitrate & nitrite
3 productsNitrate and nitrite, often from agricultural runoff, fertilizer, or septic systems.None of 3 verified for Nitrate & nitrite yetTreatsReverse osmosis and certified anion-exchange systems reduce nitrate and nitrite in drinking water.Does not solveActivated-carbon filters, pitchers, and water softeners do not remove nitrate, and boiling concentrates it rather than removing it.Certification to checkNSF/ANSI 58Look for NSF/ANSI 58 (reverse osmosis) carrying a specific nitrate/nitrite reduction claim, or an anion-exchange unit whose certifier listing names nitrate/nitrite.Nitrate & nitrite: products and evidence →Arsenic
3 productsNaturally occurring arsenic that can leach into groundwater across many regions.None of 3 verified for Arsenic yetTreatsReverse osmosis and arsenic-selective adsorptive media reduce arsenic at the treated tap.Does not solveCarbon filters and softeners do not reliably remove arsenic, and arsenic-III (arsenite) often needs oxidation to arsenic-V before it can be filtered.Certification to checkNSF/ANSI 58Look for NSF/ANSI 58 with a pentavalent arsenic (arsenic V) reduction claim, and check whether your water carries arsenic III, which needs a pre-oxidation step.Arsenic: products and evidence →Fluoride
6 productsFluoride, whether added for dental health or naturally elevated in some groundwater.5 of 6 with current certification evidence for FluorideTreatsReverse osmosis and activated-alumina systems reduce fluoride in drinking water.Does not solveStandard carbon pitchers, faucet filters, and softeners do not reduce fluoride, and boiling concentrates it rather than removing it.Certification to checkNSF/ANSI 58Look for NSF/ANSI 58 (reverse osmosis) with a fluoride reduction claim, or an activated-alumina unit rated for fluoride.Fluoride: products and evidence →Before you buy
Certification matters more than category.
A filter certified for chlorine is not automatically certified for PFAS or lead. Match the exact model’s certified claim to the problem in your water. Test or check your system’s records first.