What it is, whether to worry, and what removes it.
Every contaminant on this site gets two pages: an explainer that answers whether you should worry, and a roundup that answers what removes it. Certification is the dividing line throughout — a filter is only proven against the contaminants it is specifically certified for.
People arrive at this hub because of a headline, a neighborhood rumor, a note from the utility, or a doctor. The name is already in their head. What they need is whether it warrants the worry, and what genuinely removes it.
So every contaminant here gets two pages rather than one. The explainer answers should I worry. The roundup answers what removes it. They are split on purpose: burying the buy path under fifteen hundred words of anxiety serves nobody, and neither does a product list that never explains what it is protecting you from.
The single most useful thing to understand before reading any contaminant page is that filter certifications are contaminant-specific. A filter is not "NSF certified" in general. It is certified against a particular standard, for a particular list of contaminants, at particular concentrations. Marketing language blurs this constantly, and the blur is where money gets wasted.
| Standard | What it actually covers | Is it a health claim? |
|---|---|---|
| NSF/ANSI 42 | Aesthetic effects: taste, odor, chlorine | No |
| NSF/ANSI 53 | Health effects: lead, cysts, VOCs, chromium, certain PFAS and others | Yes |
| NSF/ANSI 58 | Reverse osmosis systems: arsenic, barium, fluoride, lead, nitrate, radium, selenium, TDS | Yes |
| NSF/ANSI 401 | Emerging compounds at trace level, e.g. pharmaceuticals | Yes |
| NSF P473 | A protocol specific to PFOA and PFOS | Yes |
The practical consequence is blunt: a pitcher certified to NSF/ANSI 42 is an excellent answer to a chlorine taste and no answer at all to lead. A pitcher certified to 53 for lead may still have no PFAS certification. The Brita Elite is exactly that case, and it is the most common mismatch we see.
Some of the best-performing filters on the market are tested to NSF standards rather than certified under them. That is not a scam, and it is not equivalent either. Testing means an independent lab ran the standard's method and published the result. Certification means a listing body verified it and keeps verifying it, with the product listed publicly.
Clearly Filtered and Epic both fall in the tested-to camp, and both have genuinely broad results. If you need a listing you can point a landlord or a lender at, that distinction decides your purchase. If you are satisfied by published test data, it probably does not. Either way you should know which one you are buying, and this site says so on every product.
The negative cells in this matrix matter as much as the positive ones. Telling somebody that a pitcher will not fix their rotten-egg smell is the honest answer, and it is the one most sites skip.
| Contaminant | Pitcher | Under-sink / RO | Whole-house | Well |
|---|---|---|---|---|
| Lead | Yes, certified models only | Yes | Rarely appropriate | Yes |
| PFAS | Yes, certified models only | Yes — RO strongest | Yes | Yes |
| Chlorine / chloramine | Yes | Yes | Yes | No — wells are not chlorinated |
| Iron and sulfur | No | Limited | Yes | Yes — primary |
| Hardness | No | No | Softener, not a filter | Yes |
We do not tell you your water is dangerous in order to sell you a filter. Several contaminant pages on this site conclude that for most readers, on most supplies, the honest answer is "probably not a problem for you, and here is how to check." Chlorine is the clearest example: the taste is genuinely annoying and the health case for removing it at typical municipal levels is thin. We say so on the page.
We also date every certification claim. Manufacturers revise performance data sheets, and a certification that was accurate last year may not be accurate now. Each page carries the date we last checked, and corrections are logged publicly when we get something wrong.
Each of these ends in a specific product, a live price where one exists, and a link that goes straight to the retailer.
Best for leadWater Filters Certified For LeadCertified under NSF/ANSI 53 or 58 for lead. Pitcher, under-sink and renter options.Our pick: Brita Elite Filter (with any Brita pitcher)
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Best for PFASFilters That Actually Address PFASThe filters with a real PFOA/PFOS certification, and the ones only tested to it.Our pick: AquaTru Classic Countertop Reverse Osmosis Purifier
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Best for chlorine tasteFilters For The Pool TasteCarbon fixes it for pennies a gallon. Chloramine is the one exception.Our pick: Brita Elite Filter (with any Brita pitcher)
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Best for iron and sulfurIron And Sulfur Systems, By The NumbersAir injection or cartridge, chosen by your ppm numbers rather than by category.Our pick: SpringWell WS1 Well Water Iron Filter (Air Injection)
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Best for hard waterFor Hard Water, Buy A SoftenerSofteners, sized from your grains per gallon. Filters genuinely cannot do this.Our pick: Whirlpool WHES40E 40,000-Grain Water Softener
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What each contaminant is, where it comes from, and whether it warrants the concern.
Lead Comes From Your PipesWhere lead actually enters, why your utility's report cannot see it, and who should test.PFAS And What The Rule Actually SaysThe 2024 rule, the 2027 monitoring deadline, and what removes PFAS at home now.
Chlorine Is There On PurposeWhy it is added, what chloramine changes, and when removing it is worth paying for.Iron, Manganese And That SmellThe well-water trio. Why oxidation is the mechanism and carbon is not.
Hard Water Is Not ContaminationMinerals, not contamination. Harmless to drink, and quietly expensive.If you are on a public supply, your utility publishes an annual Consumer Confidence Report listing detected contaminants and their levels. It is free and it is the correct starting point. It will not tell you about lead, though, because lead almost always enters from the service line or household plumbing after the utility's sample point — that requires testing at your own tap.
No, not unless it is separately certified for PFAS. NSF/ANSI 53 covers a list of health contaminants, and a product is certified for the specific ones it was tested against, not the whole list. The Brita Elite is certified for lead under 53 and is not certified for PFOA or PFOS. That is a real and common example of the gap.
It is the broadest single technology for drinking water, covering dissolved contaminants that carbon cannot touch — fluoride, nitrate, arsenic, total dissolved solids. It is not the answer to everything: it treats one tap rather than the house, it sends some water to the drain, it is slower, and it does nothing for the hardness that is scaling your water heater.
Because we do not test filters, and we will not pretend otherwise. What we can do is read certification listings, pull manufacturer performance data sheets, cite the standards, and do the cost-per-gallon arithmetic in the open. Certification is third-party evidence that a claim was verified by somebody with something to lose. Our opinion is not.