Is tap water safe to drink?
For most public water systems in the United States, yes — the water meets every enforceable federal limit. But “safe” is a property of one system and one building, not of a country, and two different things decide yours.
One thing to know before you look yours up: most systems report something above a health goal, and for many substances that goal is zero — so “above the goal” means “found at all”, not “over the limit”. The number that matters is the distance to the limit, and your page shows both.
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The first is published: your water system has to test for a defined list of contaminants and report what it finds. The second is not: nobody measures what your own pipes add after the water reaches your building — which is where lead comes from.
In our data, more than 9 in 10 of the roughly 19,700 public water systems we track — serving about 94% of the people they cover — have no violation of an enforceable limit on record.
So the useful question is not whether tap water is safe. It is what did my system find, what did it never look for, and what does my building add — and all three can be answered for your address.
“Safe” has two definitions, and they are different numbers
This is the most misread thing in drinking-water data, and almost every alarming headline about tap water rests on it.
The MCL is the enforceable limit — a legal maximum. Go above it and the utility is in violation and has to act. The MCLG is a health goal, set with no allowance for cost or feasibility. For a chemical with evidence that it may cause cancer and no dose below which it is considered safe, the EPA sets that goal to zero (EPA, How EPA Regulates Drinking Water Contaminants). Zero means no safe level is known — not that a trace amount has been shown to harm anyone.
So for those substances, “above the health goal” means “found at all”. A system reporting a trace amount and a system sitting just under the legal limit are both “above the goal”. The number that tells you whether to do anything is the distance to the limit.
- Health goal: zero
- 0 ppb
- Your system reported
- 6.2 ppb
- TTHM group limit
- 80 ppb
Four things decide the answer for your address
What your water system published
Every community water system in the US has to test for a defined list of contaminants and publish the results once a year. That report tells you what was found in the distribution system, and it is free.
What it never tested for
A substance nobody sampled looks exactly like a clean result: there is simply no row for it. This is the single most misread thing in the data, and it is why an absence of PFAS results is not the same as PFAS not being present.
What your own building adds
Lead is the clearest case. It comes overwhelmingly from the service line and the pipes inside your building rather than from the source, so a clean system-wide result says little about a house built before 1986. No published data can answer this one for you.
Who is drinking it
Several limits are set with a margin for the general population. Infants, pregnancy and a compromised immune system change which findings matter — and often change nothing at all, which is also worth knowing.
Common questions
- Why do people say not to drink tap water?
- Three reasons, and they are not equally good. Flint made it obvious that a utility can fail and that residents can be told the water is fine while it is not. PFAS turned up in systems that had never tested for it, so an old clean record stopped being reassuring. And chlorine tastes like chlorine, which people read as contamination when it is actually the disinfection working. None of those makes tap water unsafe in general. All three make “check yours” the right answer.
- Which is safer, tap or bottled water?
- Not inherently either. Bottled water is regulated as a food product rather than under the drinking-water rules, and a great deal of it is treated municipal water. It is a reasonable short-term answer during a boil-water advisory. It is an expensive answer to a problem a certified filter usually solves for less, and it does nothing about the water you shower in.
- Do I really need to filter my tap water?
- Often not. A filter is worth buying when it addresses something your data actually shows, or something your data cannot see — lead from your own plumbing being the common case. Match the NSF/ANSI standard to the finding rather than buying on a “removes 99% of contaminants” claim, which means nothing on its own. Where nothing in the record warrants treatment, nothing is a legitimate answer.
- Which US state has the safest tap water?
- There is no single answer, because “safest” depends on what you measure — violations, detections above a health goal, or the substances a state happens to test for. States differ more in how much they test than in what they find. We publish state-by-state rankings and say which measure each one uses, so you can see the answer to the question you actually care about.
- Which US city has the cleanest tap water?
- Same caveat, and it matters more at city level: a city with very few tests can look cleaner than a city that tests thoroughly, because a substance nobody sampled produces no row. Any ranking that does not say what it measured is not telling you much. Ours says.
- Is my state's tap water OK to drink?
- Almost always the answer is about your system, not your state — two towns an hour apart can draw from different sources and treat them differently. Start with your own city and the answer takes one search.
Why do people say not to drink tap water?
Three reasons, and they are not equally good. Flint made it obvious that a utility can fail and that residents can be told the water is fine while it is not. PFAS turned up in systems that had never tested for it, so an old clean record stopped being reassuring. And chlorine tastes like chlorine, which people read as contamination when it is actually the disinfection working. None of those makes tap water unsafe in general. All three make “check yours” the right answer.
Which is safer, tap or bottled water?
Not inherently either. Bottled water is regulated as a food product rather than under the drinking-water rules, and a great deal of it is treated municipal water. It is a reasonable short-term answer during a boil-water advisory. It is an expensive answer to a problem a certified filter usually solves for less, and it does nothing about the water you shower in.
Do I really need to filter my tap water?
Often not. A filter is worth buying when it addresses something your data actually shows, or something your data cannot see — lead from your own plumbing being the common case. Match the NSF/ANSI standard to the finding rather than buying on a “removes 99% of contaminants” claim, which means nothing on its own. Where nothing in the record warrants treatment, nothing is a legitimate answer.
Which US state has the safest tap water?
There is no single answer, because “safest” depends on what you measure — violations, detections above a health goal, or the substances a state happens to test for. States differ more in how much they test than in what they find. We publish state-by-state rankings and say which measure each one uses, so you can see the answer to the question you actually care about.
Which US city has the cleanest tap water?
Same caveat, and it matters more at city level: a city with very few tests can look cleaner than a city that tests thoroughly, because a substance nobody sampled produces no row. Any ranking that does not say what it measured is not telling you much. Ours says.
Is my state's tap water OK to drink?
Almost always the answer is about your system, not your state — two towns an hour apart can draw from different sources and treat them differently. Start with your own city and the answer takes one search.
Where does your state rank?
Rankings are the most-asked question about tap water and the most abused. Ours says what it measures, and it will tell you when a state simply tests less than its neighbours.
When the answer is “not right now”
Your system is under a boil-water advisory
Then it is not safe to drink untreated, today, and the utility will say so. Advisories are usually short and usually follow a main break or a loss of pressure. Current advisories
Your building has a lead service line
The system's own results cannot clear your tap. Running the water before drinking helps; a filter certified to NSF/ANSI 53 for lead removes it.
You are on a private well
Private wells sit outside the federal drinking-water rules entirely. Nobody tests them for you and nobody publishes the results — testing is the only way to know. Private well water
Your utility has a current violation
A violation means an enforceable limit was actually exceeded, which is a different thing from a result sitting above a health goal. That is the case where the number genuinely matters.
Check your own address
18,130 cities · every US state · free, no sign-up, no email
Everything above is free, and it is most of the answer
Look up your city and you get the full contaminant table, each result against its limit and its health goal, and any violations on record — no sign-up, no email. If what you want is somebody to read that record and tell you which two or three findings actually warrant a decision, we also write that up. It is not needed for most addresses, and that page says so.
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