Water filtration guide—filter for what's in your water, not for what's on the box.
Most water filter buying guides recommend products. This one explains certifications — because the right filter depends entirely on what your utility is actually delivering, and no single filter addresses everything.
NSF 42, NSF 53, and NSF 58 are the three certification numbers that tell you what any filter actually removes. A pitcher filter certified to NSF 42 improves taste. It does not remove lead. A reverse osmosis system certified to NSF 58 removes PFAS. A carbon block certified to NSF 53 removes lead but not fluoride. The box won't always tell you this clearly.
Every guide here is built on NSF International certification data, EPA SDWIS monitoring results, and peer-reviewed filtration research. No brand recommendations, no affiliate links. Guides cover pitcher filters, reverse osmosis, carbon block, whole-home filtration, chloramine removal, nitrate filters, microplastics, water softeners, chromium-6, and more—matched to what EPA SDWIS data shows is actually in your water.
Filtration guides
Chloramine in tap water — what it is and how to remove it
About one-third of US utilities use chloramine instead of chlorine as a disinfectant. Unlike chlorine, chloramine doesn't evaporate—it requires a specific filter type to remove. How to check if your utility uses it and what actually addresses it.
Microplastics in drinking water — what we know and what to do
Microplastics have been detected in US tap water but remain unregulated. What the current research shows on health effects, which filter types reduce them, and how to check your utility's monitoring status.
Water softener vs water filter — what's the difference?
Does a water softener remove chlorine, lead, PFAS, or nitrates? Water softeners treat hardness—they don't remove most contaminants people are concerned about. What each system does and when you need both.
Does a Brita filter lead?
Does a Brita filter lead, PFAS, or TTHMs? Standard Brita pitchers are NSF 42 certified—they improve taste but aren't certified to remove lead or PFAS. What the certification numbers mean and what filter you actually need.
PFAS water filters — what actually removes forever chemicals
What water filter actually removes PFAS? Reverse osmosis (NSF 58) removes 90–99%. NSF 53 carbon block removes most long-chain PFAS. Standard pitcher filters are not certified for PFAS removal. How to choose based on your water report.
Lithium in drinking water
Lithium in drinking water—detected nationwide for the first time under EPA UCMR5. No federal limit exists yet. Who should be cautious, what levels have been found, and which filter types actually remove it.
Coming soon
Does boiling water remove lead, PFAS, or nitrates?
Coming soonDoes boiling water remove lead, PFAS, chlorine, or nitrates? Boiling concentrates most dissolved contaminants rather than removing them. What heat actually does to each contaminant—and when boiling is and isn't useful.
Reverse osmosis vs under-sink carbon filter
Coming soonReverse osmosis vs under-sink carbon filter—what's the difference? RO removes PFAS, fluoride, nitrate, and arsenic. Carbon block is cheaper with narrower coverage. How to decide based on your actual contaminant profile.
Whole-home water filtration — when it's worth it
Coming soonWhole-home water filtration—when is it worth it? Point-of-entry vs point-of-use, what whole-home systems actually address, and the contaminant profiles that justify the cost vs those where it's overkill.
Water filter pitchers — what they actually remove
Coming soonBest water filter pitcher for lead, PFAS, fluoride, and chlorine—what each pitcher type removes, what NSF certification to look for, and how to match a pitcher to your utility's contaminant profile.
Nitrate filter — which systems actually work
Coming soonStandard pitcher filters and carbon block filters do not remove nitrates. Reverse osmosis does. What nitrates are, why they matter especially for infants, and which filter certifications cover nitrate removal.
Chromium-6 water filter — what removes hexavalent chromium
Coming soonChromium-6 (hexavalent chromium) is unregulated at the federal level despite documented carcinogenicity. Which filter certifications address it, what your utility's data shows, and how California's stricter MCL compares to the federal standard.
The numbers that matter
NSF certification—what each number actually means
NSF International independently certifies that a filter removes what it claims to remove. The certification number tells you which category of contaminants was tested—a filter certified to NSF 42 was never tested for lead, regardless of what the marketing says.
Removes
Chlorine, taste, odour, particulates
Does not cover
Lead, PFAS, nitrate, TTHMs, heavy metals
Typical filters
Most pitcher filters (Brita standard), refrigerator filters
Removes
Lead, cysts, select VOCs, some heavy metals, TTHMs
Does not cover
PFAS, nitrate, fluoride, arsenic (usually)
Typical filters
Solid carbon block filters (countertop, under-sink)
Removes
PFAS (90–99%), nitrate, fluoride, arsenic, lead, most heavy metals
Does not cover
Some volatile organics (depends on post-filter)
Typical filters
Under-sink RO systems, countertop RO
Removes
Pharmaceuticals, microplastics, select personal care product chemicals
Does not cover
PFAS (requires NSF 58), heavy metals (requires NSF 53)
Typical filters
Select activated carbon and RO systems with this additional rating
A filter can hold multiple NSF certifications. An under-sink carbon block certified to both NSF 42 and NSF 53 removes chlorine and lead. A reverse osmosis system certified to NSF 58 typically also carries NSF 42 and NSF 53. Always look for the specific certification on the NSF product database —not just the marketing claim on the box.
The right starting point
The filter you need depends on what your utility is actually delivering.
PFAS detected? You need NSF 58 (reverse osmosis). Lead concern? NSF 53 solid carbon block. High TTHMs? NSF 53 also addresses those. If your utility report shows everything within limits, an NSF 42 pitcher filter may be all you need—and spending more adds nothing.
A free ZIP-code report shows your utility's actual detected levels—so you can match the filter to the problem, not to the marketing.
For households that want a personalised filter recommendation based on their specific water report—or are considering a more comprehensive water treatment system—a free consultation is available through Drawn Health.
Book a free consultation →Free · No email required
What does your tap water actually contain?
Enter your ZIP code to see your utility's detected contaminant levels—PFAS, lead, nitrates, TTHMs, and more—compared against EPA limits and EWG health guidelines. Then you'll know which filter certification you actually need.
Check your water →