Guides
Every guide cites its sources. Drafts are marked and stay out of search engines until our editor has checked them.
- The lowest-cost ways to get a certified PFAS filter
No prices, just running-cost facts: filter type, rated gallons and cartridges a year for the 11 filters whose PFAS claim an IAPMO listing backs.
- Chloramine in tap water
What chloramine is, why utilities use it, who needs to remove it, and the NSF/ANSI 42 chloramine claim to look for on a filter listing.
- Does reverse osmosis remove PFAS?
Reverse osmosis is one of the most effective home treatments for PFAS. What EPA says, what to look for on the label, and 4 RO units with a PFAS listing.
- Hard water, skin and hair: what the evidence says
Hard water is not a health hazard, but some studies link it to eczema in children. What softener trials and lab studies on hair actually found.
- How to read your water quality report (CCR)
What each part of your utility's yearly water quality report means, how to compare a result with its limit, and where lead, PFAS and lithium show up.
- How we decide "certified"
A filter claim counts as certified here only when a certifier's public listing shows it for that exact model. How we check, and what we never do.
- IAPMO vs NSF vs WQA
IAPMO R&T, NSF and WQA all certify home filters to the same NSF/ANSI standards. How they publish listings, and why a filter may appear in only one.
- Lead pipes and lead filters
How to find out if a lead service line feeds your home, what EPA's 2024 lead rule requires, and how to pick a filter certified to NSF/ANSI 53 for lead.
- Lithium in tap water
UCMR 5 found lithium in many US water systems. EPA has no limit, only a 10 µg/L screening level, and none of the 97 filters we track is certified to reduce it.
- NSF/ANSI 42 vs 53 vs 58 vs 401 vs P473 explained
What NSF/ANSI 42, 53, 58 and 401 cover, where the old P473 PFOA/PFOS test went, and why 61 and 372 say nothing about what a filter removes.
- PFOA and PFOS limits explained
EPA's 4.0 ppt limits for PFOA and PFOS, the 2029 deadline, the 2026 proposals on the other four PFAS limits, and what UCMR 5 testing found.
- Pitcher filters compared by certification
Lead and PFAS certification status for 19 pitcher and countertop dispenser filters, from IAPMO R&T listings checked 16 Oct 2026.
- Salt vs salt-free softeners
Salt softeners take hardness out of the water; salt-free units leave it in. How each works, what each certification covers and what brands cite.
- Softener sizing for well water
On a well, test hardness, iron, manganese and pH before sizing a softener. The iron adjustment makers print, and the iron limits of common models.
- TDS meters: what they can't tell you
A TDS meter estimates dissolved minerals from conductivity. It cannot identify contaminants, see germs, or detect lead or PFAS at EPA's limits.
- Under-sink reverse osmosis compared by certification
Lead and PFAS certification status for 24 under-sink and countertop reverse osmosis systems, from IAPMO R&T listings checked 16 Oct 2026.
- Filter replacement schedules
How long filter cartridges last in gallons and months, how many replacements a year each filter type needs, and how to work out your own.
- Well water testing
Public water data and EPA limits do not cover private wells. What to test a well for every year, when to test for more, and where to get it done.
- What size water softener do I need?
Size a softener from hardness, people, daily use and days between regenerations, then check its capacity at the salt setting you will use.
- Whole-house vs under-sink vs pitcher filters
Pitchers and under-sink filters treat one tap; whole-house filters treat every tap. What each type can be certified for, and what IAPMO lists.