Guides, answer first.

Each one starts with the answer, then shows its work. Every limit comes from EPA and every standard from NSF.

• Do water filters remove PFAS?Some filters reduce PFAS: activated carbon, reverse osmosis and ion exchange can all work. Look for a PFOA and PFOS reduction claim under NSF/ANSI 53 or 58 on a certifier's listing. EPA notes that today's certifications do not yet show a filter reaches its new 4.0 ppt limits, and a filter only works if you replace it on schedule.Updated Oct. 4, 2026 · 2 min read
• How to read your water quality reportFind the table of detected contaminants. Compare each level with two columns: the MCL, the legal limit the utility must meet, and the MCLG, EPA's health goal. A level under the MCL is legal. A level above the MCLG is worth understanding. Then read the violations section.Updated Oct. 4, 2026 · 3 min read
• How to test well waterTest a private well every year for total coliform bacteria, nitrates, total dissolved solids and pH, using a laboratory certified for drinking water. Test again right away if anything changes: the taste, the color, a flood, new well parts, or a problem reported nearby.Updated Oct. 4, 2026 · 2 min read
• NSF 42 vs 53 vs 58 vs 401, decodedNSF/ANSI 42 covers taste, odor and appearance, such as chlorine. 53 covers health contaminants such as lead, cysts, VOCs and PFOA/PFOS. 58 is for reverse osmosis systems, which must reduce total dissolved solids and may hold other claims. 401 covers 15 named trace chemicals plus microplastics. A filter is certified only for the claims on its listing.Updated Oct. 4, 2026 · 3 min read