Most Americans can check their tap water safety in under a minute. Enter your zip code into the KnowYourExposure tool to see EPA-tested PFAS, lead, and nitrate levels for your water system. If any contaminant exceeds the EPA's maximum contaminant level, a certified filter can reduce exposure by 90% or more. Below, we walk through exactly how to read your results and what to do next.
At least 45% of U.S. tap water is estimated to contain one or more PFAS, according to U.S. Geological Survey research published in 2023 that sampled taps at 716 locations. That estimate covers only the 32 PFAS the USGS could measure, out of thousands in commercial use.
The question "is my water safe to drink" is the single most common thing people type into Google about their tap water – and the answer depends on your zip code, your water utility, and which contaminants you're worried about. We built KnowYourExposure to make that answer easy to find. This guide shows you how to check, what the numbers mean, and what to do if your water doesn't pass.
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You don't need to mail a sample to a lab to get a first read on your water quality. The EPA already tests public water systems across the country, and that data is public. Here's how to use it:
Step 1: Enter your zip code. Go to KnowYourExposure.com and type in your zip code. The tool pulls EPA UCMR5 data for every water system that serves your area and shows you which contaminants were detected and at what levels.
Step 2: Compare to EPA limits. The tool flags anything that exceeds the EPA's maximum contaminant levels (MCLs). For PFAS, the new enforceable limit is 4 parts per trillion (ppt) for PFOA and PFOS individually. For lead, the action level is 15 parts per billion (ppb). For nitrates, it's 10 milligrams per liter.
Step 3: Read the details. Click into any flagged contaminant to see the specific test results, the date they were collected, and context on what that exposure level means. If you want a printable breakdown, you can get a detailed water quality PDF report for your address.
Step 4: Decide on next steps. If your water is clean across the board, you're good. If something's elevated, scroll down – we cover filters and other actions below.
Not every contaminant is equally dangerous, and not every detection means your water is unsafe. Here are the ones that matter most in 2026, ranked by how many people they affect and how serious the health risks are.
PFAS are synthetic chemicals that don't break down in the environment or in your body. The EPA's UCMR5 testing program sampled about 10,000 public water systems between 2023 and 2025, and about a third (34%) showed detectable PFAS levels. In April 2024, the EPA set the first-ever enforceable limits: 4 ppt for PFOA and 4 ppt for PFOS. Systems have until April 2029 to comply, and in 2026 the EPA proposed letting systems that apply push that deadline to 2031, which means many are still serving water above those limits right now.
Health risks from PFAS exposure include increased cancer risk (particularly kidney and testicular), thyroid disruption, immune system suppression, and developmental effects in children. We cover the full breakdown in our PFAS contamination guide. If you live near a military base, your risk is higher – DoD sites are among the most contaminated in the country.
Lead gets into water from old pipes and service lines, not from the source water itself. The EPA's latest estimate, built from service line inventories utilities submitted in 2025, puts the number of lead service lines still in use at about 4 million, down from the 9.2 million the agency projected in 2023 from a smaller sample of systems. There is no safe level of lead exposure for children, and even low levels are linked to IQ reduction, behavioral problems, and developmental delays.
The EPA's action level for lead is 15 ppb, but the American Academy of Pediatrics recommends water in schools contain no more than 1 ppb. If your home was built before 1986, lead pipes are a real possibility. You can check for lead in your drinking water using our tool and your water system's consumer confidence report.
Nitrates come from agricultural runoff – fertilizer and animal waste seeping into groundwater. The EPA limit is 10 mg/L, and most urban systems stay well below that. But rural areas with private wells or small water systems can see spikes, especially during spring and after heavy rain. Nitrates are particularly dangerous for infants, causing a condition called methemoglobinemia (blue baby syndrome) that reduces the blood's ability to carry oxygen.
Every public water system in the U.S. is required to publish an annual Consumer Confidence Report (CCR). Your utility mails it once a year or posts it online. The problem is that most CCRs are written in regulatory language that's hard to parse. Here's what to look for.
Find the table that lists detected contaminants. Each row shows the contaminant name, the level detected (usually as a range or average), the MCL (the legal limit), and the MCLG (the goal – often zero for carcinogens). If the detected level is below the MCL, your water meets federal standards. If it's below the MCLG, it meets the health-based goal. These are two different bars, and the MCLG is the stricter one.
Pay attention to the date. CCRs report last year's data, and testing happens on a schedule – some contaminants are tested quarterly, others annually or even less often. The UCMR5 data on KnowYourExposure can sometimes be more current than your CCR for specific contaminants like PFAS.
The EPA uses several different numbers for the same contaminant, and they mean very different things. Understanding the difference matters because your water can be "legal" while still posing health risks.
The MCL (Maximum Contaminant Level) is the enforceable legal limit. Utilities must keep contaminant levels below this number or face violations. MCLs factor in cost and feasibility of treatment, not just health – so they're often higher than what's strictly safe.
The MCLG (Maximum Contaminant Level Goal) is the health-only target. For carcinogens, the MCLG is usually zero. For lead, it's zero. The MCLG represents the level at which there's no known health risk, but it's not enforceable.
Health Advisories are non-enforceable recommendations the EPA issues when science suggests a concern but a formal MCL hasn't been set. Before the 2024 PFAS rule, the only federal guidance for PFAS was a 2022 interim health advisory of 0.004 ppt for PFOA, 17,500 times lower than the old 2016 advisory of 70 ppt. That massive revision shows how quickly the science is moving.
If your water shows detectable PFAS, any lead above 1 ppb, or nitrates above 5 mg/L (half the legal limit), a filter is worth the investment. Even if your water meets all federal limits, a filter adds a margin of safety – and for contaminants like lead where no level is safe, getting as close to zero as possible makes sense.
Not all filters remove all contaminants. Here are three options at different price points, each tested and certified for the contaminants that matter most.
The Brita Elite is certified to NSF/ANSI 42, 53 and 401 for lead and more than 30 other contaminants, though Brita's current data sheet makes no PFAS claim. It won't catch everything – pitcher filters have limits – but at around $35 for the pitcher and $7 per replacement filter, it's the lowest-friction option. Good for apartments, dorm rooms, or anyone who wants a first line of defense without a major investment.
The AquaTru is a countertop reverse osmosis system – no plumbing needed. It removes up to 99.9% of PFAS, lead, chromium-6, and dozens of other contaminants. Independent testing by IAPMO confirmed its PFAS removal claims. At around $450 upfront with annual filter costs of roughly $100, it's a serious step up from a pitcher but still doesn't require a plumber.
The Big Berkey is a countertop, gravity-fed stainless steel system that filters 2.25 gallons at a time. Berkey's published lab tests (not an NSF/ANSI certification) report that it removes more than 99.9% of PFOA and PFOS using its Black Berkey elements. It costs around $350 and doesn't need electricity or water pressure, which makes it popular for both everyday use and emergency preparedness. Filter elements last for up to 6,000 gallons before needing replacement.
For a full comparison of filter types and certifications, see our water filtration options guide.
If you live within 10 miles of a military installation, your water contamination risk is measurably higher. The Department of Defense has identified more than 700 military installations that need assessment for PFAS use or release, much of it from firefighting foam (AFFF) used in training exercises. According to the DoD's own status report, as of September 30, 2024, 574 of 722 installations had moved on to a full remedial investigation after initial sampling.
Camp Lejeune in North Carolina is the most publicized case – decades of contamination led to a federal health study linking the base's water to cancers, birth defects, and other conditions. But Camp Lejeune is not an outlier. Bases across the country, from Pease Air Force Base in New Hampshire to Peterson Space Force Base in Colorado, have similar contamination profiles.
We track military base water contamination data for every DoD installation with published PFAS results. If you live near a base, check both your municipal water data and the base-specific data – contamination plumes can extend miles from the source.
The EPA's Fifth Unregulated Contaminant Monitoring Rule (UCMR5) is the largest systematic PFAS testing program ever conducted in the United States. Between January 2023 and December 2025, the EPA required water systems serving more than 3,300 people – plus a sample of smaller systems – to test for 29 PFAS compounds plus lithium and other emerging contaminants.
The results are sobering. According to EPA UCMR 5 data (2023-2025), about 34% of tested systems detected at least one PFAS compound. About 16% of systems had at least one sample at or above the new 4 ppt MCL for PFOA or PFOS. And because only systems serving 3,300+ people were required to test, smaller rural systems – which often have less treatment infrastructure – are largely absent from the data.
The KnowYourExposure tool pulls directly from the UCMR5 dataset, so when you check your water quality by zip code, you're seeing the same results your water utility reported to the EPA. If your system hasn't been tested under UCMR5, we note that too – no data doesn't mean no contamination.
Everything above applies to public water systems. If your home runs on a private well, none of this federal testing covers you. The EPA doesn't regulate private wells, and no federal law requires well water testing. According to the USGS, roughly 23 million U.S. households rely on private wells, and most have never been tested for PFAS.
If you're on a well, your only option is to test it yourself. State health departments often offer subsidized testing, and certified labs like Eurofins and SimpleLab's Tap Score can test for PFAS, lead, nitrates, and bacteria. Expect to pay $100-$300 for a panel that covers the basics.
Start with data. Check your water quality by zip code to see what EPA testing has found in your area. Look at the specific contaminants detected, compare them to the EPA limits we described above, and decide whether a filter makes sense for your household.
If you want a more detailed breakdown, including contaminant trends over time and comparisons to national averages, get a detailed water quality PDF report for your address. We pull from the same EPA datasets and present the numbers in plain language.
Clean water shouldn't require a chemistry degree to verify. We built this tool because the data exists – it's just buried in federal databases that no one reads. Your zip code is all it takes to find out where you stand.
How do I know if my tap water is safe to drink? Enter your zip code into a water quality lookup tool like KnowYourExposure.com to see EPA-tested contaminant levels for your water system. You can also request your utility's annual Consumer Confidence Report, which lists every detected contaminant and whether it meets federal limits. If any contaminant exceeds the EPA's maximum contaminant level, consider a certified water filter.
What does UCMR5 mean for my water? UCMR5 is the EPA's Fifth Unregulated Contaminant Monitoring Rule, which required about 10,000 water systems to test for 29 PFAS compounds between 2023 and 2025. About 34% of tested systems detected at least one PFAS compound. You can see your system's UCMR5 results by entering your zip code at KnowYourExposure.com.
What is the safest water filter for PFAS? Reverse osmosis systems remove up to 99.9% of PFAS from drinking water. The AquaTru countertop RO system and Big Berkey gravity filter both have independent lab tests confirming PFAS removal. Certified activated carbon filters can reduce PFOA and PFOS, but they are less effective than RO for the full range of PFAS chemicals.
Is bottled water safer than tap water? Not necessarily. The FDA regulates bottled water less strictly than the EPA regulates tap water, and Consumer Reports' 2020 testing of 47 bottled waters measured PFAS in several popular brands. Tap water with a certified filter is generally a safer and more cost-effective option than bottled water for daily drinking.
Does boiling water remove PFAS? No. Boiling is not a reliable way to remove PFAS, and because some of the water evaporates while most of the chemicals stay behind, it can slightly concentrate them. Filtration through reverse osmosis or activated carbon is needed to reduce PFAS levels.