Before you buy a water filter, answer one question first: what’s actually in your water?
Filter claims are everywhere: better taste, lead reduction, PFAS, dissolved solids, hard water. But every home’s water is different, and no single filter is designed to handle everything.
I’m Ree Fonteyn, and my approach is simple: find out what’s in your water, decide what you want to reduce, then look for a filter independently certified for that purpose. I research certifier listings, manufacturer documents, replacement filter costs and customer-feedback themes. I don’t lab-test or home-test products.
Start with your water, not a filter
A filter should solve a problem you can identify, not one you have to guess at.
- Chlorine taste or smell? A filter certified for chlorine taste and odor may be enough.
- Worried about lead? Look for a system certified specifically for lead reduction.
- Hard water? A water softener solves a different problem than a drinking water filter.
- PFAS? You need evidence the exact system is certified to reduce the PFAS you care about.
A pricier filter isn’t automatically a better fit, and a certification for one contaminant doesn’t cover everything else. You can read more about my method on How We Review.
On city water? Read your Consumer Confidence Report
If you’re on a public water system, your first stop is its annual Consumer Confidence Report (CCR). It explains where your water comes from and which regulated contaminants were detected during monitoring. Start at the EPA’s Consumer Confidence Reports page, or check your utility’s website. Your water bill will name your utility.
When you read it, look for:
- Which contaminants were detected, at what levels and in what units.
- Whether any legal limit was exceeded. Reports compare levels with federal Maximum Contaminant Levels (MCLs).
- Lead. Lead often comes from service lines and household plumbing, so a utility-wide report can’t tell you the level at your own faucet.
- Violations or treatment changes your utility explains.
A CCR isn’t a personal test of your tap, and it doesn’t cover every possible contaminant. If you have a specific concern it doesn’t answer, consider targeted testing through a certified lab. If your utility issues a boil-water or do-not-drink advisory, follow it. Don’t assume a household filter makes the water safe.
Cross-check with the EWG Tap Water Database
The EWG Tap Water Database lets you search by ZIP code or utility. I treat it as a second opinion, not a replacement for your CCR.
One important caveat: EWG compares levels with its own health guidelines, which are stricter than federal legal limits. A contaminant can sit above an EWG guideline while your utility is fully compliant with the law. That doesn’t make EWG wrong or your utility negligent. They’re measuring against different benchmarks.
Use both: your CCR for official results and compliance, EWG for extra context. The goal isn’t to be alarmed by every number. It’s to work out which concerns actually apply to your water.
On a private well? Test it yourself
Private wells aren’t regulated like public water systems, so testing and upkeep are up to you. The EPA’s Private Drinking Water Wells guide is the best place to start.
What to test: EPA recommends testing every year for total coliform bacteria, nitrates, total dissolved solids and pH. Depending on your area, you may also need arsenic, lead, iron and manganese, pesticides, PFAS or other local contaminants. Your state or local health department can tell you what’s relevant where you live.
When to test again: if the water’s taste, smell or color changes, after well repairs, after flooding, or if there’s a new contamination concern nearby.
Where to test: use a state-certified drinking water lab certified for the tests you need, and follow its sampling instructions. Then choose treatment based on your results, not a general-purpose filter and hope.
Match the problem to a certified filter type
Once you know your main concern, narrow down the type of treatment. This table is a starting point. Not every product in a category is certified for every contaminant listed, so always check the exact model.
| Your concern | Treatment type to consider | Standard to look for | My guide |
|---|---|---|---|
| Hard water and scale | Water softener | NSF/ANSI 44 | Best Water Softeners |
| Lead | Under-sink RO or lead-certified filter | NSF/ANSI 53 or 58, with a lead-reduction claim | Best Under-Sink RO |
| PFAS (e.g. PFOA/PFOS) | Certified RO or carbon filter | NSF/ANSI 53 or 58 with a PFOA/PFOS or Total PFAS reduction claim | Best Under-Sink RO |
| High total dissolved solids (TDS) | Reverse osmosis | NSF/ANSI 58 | Best Under-Sink RO |
| Chlorine taste or odor | Carbon pitcher | NSF/ANSI 42 | Best Water Filter Pitchers |
| Lead, but you prefer a pitcher | Pitcher certified for lead | NSF/ANSI 53 with a lead-reduction claim (NSF/ANSI 401, if listed, covers certain emerging compounds, not lead) | Best Water Filter Pitchers |
A few things to keep in mind:
- A softener isn’t a drinking water filter. It targets hardness minerals, not lead or PFAS.
- RO isn’t always necessary. It reduces a broad range of dissolved contaminants, but it produces reject water and needs maintenance. For chlorine taste alone, a certified carbon filter may be more practical.
- Pitcher certifications vary widely. Some cover only taste and odor; others add specific health-related claims.
- Wells can need more. Bacteria, iron, manganese and sediment may need treatment beyond these three guides, plus professional advice.
How to check a certification claim
“NSF certified,” “independently tested” and “tested to NSF standards” don’t mean the same thing.
- Certified means an accredited third-party body has evaluated a specific model for specific listed claims, with ongoing checks. It isn’t a blanket endorsement.
- “Tested to” a standard means someone ran tests against that standard. Without a certifier listing, it isn’t certification. A full lab report can still be useful evidence, but I don’t treat it as equal.
Quick guide to the standards you’ll see most:
- NSF/ANSI 42: taste and odor, such as chlorine
- NSF/ANSI 53: health-related contaminants, limited to the listed claims
- NSF/ANSI 58: reverse osmosis systems
- NSF/ANSI 401: up to 15 emerging compounds, such as certain pharmaceuticals, pesticides and BPA (not lead or PFAS)
- PFAS: PFOA/PFOS and “Total PFAS” reduction claims are now certified under NSF/ANSI 53 and 58 (they replaced the older NSF P473 protocol)
- NSF/ANSI 44: residential cation-exchange water softeners (hardness)
- NSF/ANSI 372: lead content of the product’s materials, not lead reduction from water
Check the exact model in the certifier’s own directory: NSF certified drinking water treatment units, WQA or IAPMO R&T. These are separate certifiers, so an IAPMO-certified product shouldn’t be called “NSF certified.” Confirm that:
- The model number (including suffixes) matches the listing.
- The listing is current.
- The contaminant you care about is in the certified claims.
- The replacement cartridge matches the certified system.
Certification doesn’t last forever in your kitchen. Filters only perform as certified when cartridges are replaced on schedule. More on how I weigh evidence: How We Review.
PFAS
PFAS are a large family of chemicals, including PFOA, PFOS, PFHxS and PFNA. A claim for one compound doesn’t prove performance for the others. My PFAS in drinking water guide covers how to check your water, what the standards mean, and which certification claims to look for.
Questions?
My starting process in one line: know your source, check the evidence, pick your priority, match the treatment type, verify the certification, and budget for replacement filters.
If you have a question about a certification claim or a filter type, email me at contact@filteredwaterwise.com. I can’t test your water remotely or tell you whether it’s safe to drink. For suspected contamination or health concerns, contact your water utility, local health department or a certified lab.
Sources
- US EPA, Consumer Confidence Reports: https://www.epa.gov/ccr
- US EPA, Private Drinking Water Wells: https://www.epa.gov/privatewells
- Environmental Working Group, Tap Water Database: https://www.ewg.org/tapwater/
- NSF, Certified Drinking Water Treatment Units: https://info.nsf.org/Certified/DWTU/
- Water Quality Association: https://www.wqa.org/
- IAPMO R&T: https://www.iapmo.org/