Most homes don't need the most expensive system. Answer a few questions and see whether you need treatment at all — and if so, which certified option solves your documented problem at the lowest long-term cost.
Your water, in 6 questions
There are no wrong answers, and "you don't need anything" is a real result. Pick "I don't know" whenever that's the honest answer.
Every recommendation is tied to a source
We follow the public guidance, not marketing copy:
CDC — Choosing a home water filter: not every home needs a filter; different filters remove different things; many standard filters don't remove germs; poor maintenance can cause problems; point-of-use makes sense when only drinking/cooking water needs treating. cdc.gov
EPA — Home drinking water filtration fact sheet.epa.gov
NSF — Home water treatment & certification. Match the contaminant to the right NSF/ANSI standard (42 = taste/chlorine; 53 = lead & health effects; 58 = reverse osmosis; 401 = emerging contaminants incl. some PFAS; 44 = softeners). nsf.org · verify a product
How we choose — and what we won't do
We only suggest a product for a specific contaminant if it's independently certified for that contaminant. If we don't have a certified match, we say so and point you to the NSF listings — we don't guess.
We never say "removes toxins" or "healthier water" as a blanket claim. Certifications name specific substances and reduction levels; that's what we cite (and ask you to verify).
"No treatment needed" and "test first" are real, common results — not failed sales.
Costs are estimates; you can edit the key ones. Where a figure is uncertain (electricity, reject-water) we show it as a rough estimate, not false precision.
Some options below are candidates without a purchase link because we haven't joined that affiliate program yet — they're shown for completeness, not profit.
Part of Do Your Own Math
Four calculators, one rule: show the math
The Water Math is one of four independent tools. Same method, same honesty rules — no fear-selling, sources for every claim, and "you don't need to buy anything" is always an allowed answer.
What we are: a small independent project, published under a brand name rather than a person. We're anonymous by choice — but not unaccountable, which is what this page is for.
Desk-researched, not hands-on tested. This matters, so we'll say it plainly: we have not physically tested the products we point to. Our picks come from manufacturer specifications, independent certifications (NSF/ANSI, AHAM, IAPMO), published lab-style reviews and customer feedback at scale. Where we say a product is certified for something, we link you to the certifier's database — certification is model- and contaminant-specific, so check that the exact model is listed for the exact substance you care about before buying. If you want hands-on testing, read a site that does that — and then come back for the math.
How the numbers work: every calculator shows its assumptions and lets you change the ones that matter. Where published estimates disagree (they often do), we show the range rather than the flattering end, and we say which input is the least certain.
How we're funded: some links are affiliate links — if you buy, we may earn a small commission at no extra cost to you. Options shown without a link earn us nothing; we include them when they're genuinely the right answer. We never rank by commission, and the highest-paying option is regularly not our first pick.
What we won't do: claim a product removes something it isn't certified for, invent urgency, use a fake live counter, gate useful information behind an email, or tell you to buy when the honest answer is "test first" or "you don't need this".
Mistakes: we get things wrong. When we do, we change the page rather than quietly delete it — recent corrections include replacing a single water figure with an honest range, removing a life-expectancy estimate that misapplied population research, and dropping a product we couldn't stand behind. If you spot an error, we'd rather know.
Not professional advice. These are planning estimates and general information, not medical, plumbing or safety advice.
Product details last checked: 2 August 2026. Prices and availability change — always confirm on the retailer's page before buying.
📄 New: read your water report first
Your utility publishes a free yearly quality report. Ten minutes with it beats any filter ad — here's exactly which lines matter.
Every product on this page, checked against what NSF, IAPMO and the WQA actually list — the standard numbers, the reduction figures, and the gaps. One of our picks turned out to hold no certification at all for the thing we were recommending it for, so we changed the recommendation.