Arsenic
Naturally occurring, odorless, and linked to long-term cancer risk. Reduced by reverse osmosis.
Read → The Learn hub
Understand your water before you spend a dollar.
Clear, calm, sourced explanations of what is in drinking water and what the certifications“Certified” means an independent body (NSF, IAPMO, or WQA) verified the finished product against a published standard. “Tested” often just means the brand ran its own lab check — not the same thing.Learn more → really prove — so the recommendation you get from the selector actually makes sense.
One rule runs this whole site: we only call a product “certified to reduce”
a contaminant when its finished model is listed in the NSF, IAPMO, or WQA database — never on a
brand’s own lab claim. Read exactly how we verify →
Contaminants As Pb ∞ N ≈ ✛
What might be in your water
Each guide sticks to health and facts — what it is, where it comes from, the current sourced limit, and the treatment type that reduces it. No fear, no product hype.
Lead
Leaches from older pipes and fixtures. No known safe level.
Read →PFAS
“Forever chemicals.” Certified reduction covers PFOA/PFOS today.
Read →Nitrate
From fertilizer and septic systems; a concern for infants.
Read →VOCs
Industrial and fuel chemicals reduced by carbon and RO.
Read →Bacteria
A well-water disinfection issue, handled by UV.
Read → Certifications & concepts ✓ 42 R&T ◎ ⌂ ○ ▢ ★
How to read a claim like a pro
The difference between a real certification and a marketing line is the whole game. Start here.
Certified vs. tested
The single most important distinction in this category — and why we trust one and not the other.
Read →NSF/ANSI standards
What 42, 53, 58, and 401 each actually cover.
Read →IAPMO R&T
One of the accredited certifiers and how to search its database.
Read →WQA Gold Seal
What the Gold Seal means and how to look up a product.
Read →Point-of-use vs. whole-house
Where treatment belongs, by exposure route.
Read →Reverse osmosis, explained
How RO works and what it does and doesn’t remove.
Read →GPM & sizing
How flow-rate sizing keeps your pressure up.
Read →Our methodology
How we verify a product before we ever recommend it — the site’s trust anchor.
Read → NSF/ANSI standards 42 53 58 401 372 vs
Every standard, one page each
What each number certifies, what it explicitly does not, and how to verify a specific model. Start at the standards hub.
NSF/ANSI 42
Aesthetic effects — chlorine, taste, odor. Never a health claim.
Read →NSF/ANSI 53
Health effects — lead, PFOA/PFOS, cysts, VOCs and 50+ claims.
Read →NSF/ANSI 58
Reverse osmosis. Only TDS reduction is mandatory.
Read →NSF/ANSI 401
Emerging compounds — pharmaceuticals and herbicides. Not PFAS.
Read →NSF/ANSI 372
Lead content in the product — not a lead removal claim.
Read →Head-to-head
42 vs 53, 53 vs 58, and 401 vs 372 — the comparisons people search for.
Compare →Ready for your specific answer?
The selector turns all of this into one recommendation: the right system, the right size, and the honest call on whether you even need whole-house.
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