For most people in the United States, tap water is safe to drink. Public water systems serving roughly 90% of Americans are regulated by the EPA, which sets legal limits on over 90 contaminants including bacteria, heavy metals, and chemical pollutants. Utilities test continuously and must report results to customers every year. That said, safety isn’t universal. Where you live, how old your pipes are, and whether you’re on a public system or a private well all affect what’s actually coming out of your faucet.
How Tap Water Is Regulated
The EPA enforces National Primary Drinking Water Regulations that cover three broad categories: microorganisms, chemical contaminants, and disinfectants. For dangerous bacteria like E. coli and parasites like Cryptosporidium, the rules require specific treatment techniques rather than simply measuring what’s left in the water. For total coliform bacteria (a broad indicator of contamination), no more than 5% of monthly samples can test positive.
For toxic metals and chemicals, the EPA sets maximum contaminant levels. Arsenic can’t exceed 0.010 mg/L. Nitrate, which is especially dangerous for infants, is capped at 10 mg/L. Lead doesn’t have a traditional limit because no amount is considered safe. Instead, it uses an action level of 0.010 mg/L, meaning if more than 10% of sampled homes exceed that threshold, the utility must take corrective steps. Copper follows a similar approach with an action level of 1.3 mg/L.
Disinfectants like chlorine, which utilities add on purpose to kill germs, also have caps. Chlorine is limited to 4.0 mg/L. A small amount of chlorine taste or smell in your water is normal and not a health concern.
Where Safety Gaps Exist
Regulations set the floor, but problems happen between the treatment plant and your glass. The biggest concern for many households is lead, which enters water not from the source but from old pipes, solder, and service lines connecting homes to the water main. In October 2024, the EPA finalized a rule requiring water systems nationwide to identify and replace lead pipes within 10 years. If your home was built before 1986, lead plumbing is a real possibility.
Emerging contaminants also present challenges. PFAS, a group of synthetic chemicals sometimes called “forever chemicals,” have been found in water supplies across the country. These chemicals don’t break down naturally and have been linked to health problems at very low concentrations. The EPA has been moving to set enforceable limits for several PFAS compounds, but full compliance across all water systems will take years.
Arsenic contamination is a global issue too. The World Health Organization estimates that 140 million people in at least 70 countries drink water with arsenic levels above the recommended guideline of 10 micrograms per liter. In the U.S., this is most common in areas that rely on groundwater in certain geological regions, particularly parts of the Southwest.
Private Wells Are Your Responsibility
If your water comes from a private well, none of the EPA’s public water rules apply. You’re responsible for testing and maintaining your own supply. The CDC recommends testing your well at least once a year for total coliform bacteria, nitrates, total dissolved solids, and pH. You should also check your well’s physical condition every spring for mechanical problems like cracked casings or damaged seals.
Depending on your area, you may need to test for additional contaminants. Local health departments can advise whether your region has elevated risks for arsenic, lead, mercury, radium, pesticides, or volatile organic compounds like benzene and toluene. Well water can change over time due to agricultural runoff, nearby construction, or shifts in the water table, so a clean test one year doesn’t guarantee the next.
Bottled Water Isn’t Necessarily Safer
Bottled water is regulated by the FDA rather than the EPA. The FDA requires bottled water companies to protect their sources, test the water, and follow safety rules. But there’s a key difference in transparency: public utilities must deliver an annual water quality report to every customer by July 1st, detailing exactly what was found in the water. Bottled water companies have no equivalent public reporting requirement. In many cases, bottled water is simply filtered municipal tap water sold at a significant markup.
Signs Your Water May Have a Problem
Your senses can catch some issues before a lab test does. A rotten egg smell typically points to hydrogen sulfide, which can come from certain bacteria or from naturally occurring minerals in groundwater. A metallic taste often signals elevated iron, manganese, or in older homes, copper and lead leaching from pipes. Blue or green staining around faucets and drains suggests copper is dissolving from your plumbing, which can happen when water is acidic.
Not all contaminants announce themselves this way. Arsenic, nitrates, lead, and PFAS are odorless, colorless, and tasteless. Clear, pleasant-tasting water can still carry harmful levels of these substances. That’s why testing matters even when nothing seems off.
How to Check Your Water Quality
If you’re on a public system, start with your utility’s Consumer Confidence Report. The EPA requires community water systems to publish these annually, and most are available online. The report lists every detected contaminant alongside the legal limit, so you can see at a glance whether anything is close to or exceeding the threshold. Search your zip code on the EPA’s website or contact your water provider directly.
For a more detailed picture, especially if you’re concerned about what happens between the water main and your tap, you can order a certified home water test. This is particularly worthwhile if your home has older plumbing, if you’ve noticed changes in taste or appearance, or if you’re in an area with known contamination issues.
Boiling vs. Filtering
When a boil water advisory hits, bringing water to a rolling boil kills or inactivates bacteria, viruses, and parasites. It’s effective for biological threats. But boiling does nothing for chemical contaminants. It won’t remove lead, PFAS, heavy metals, or microplastics. In fact, as water evaporates during boiling, dissolved contaminants can become more concentrated in what’s left.
Filtration handles a wider range of problems. Certified filters (look for NSF/ANSI standards on the label) can reduce heavy metals, chlorine, microplastics, and parasites like Cryptosporidium and Giardia. A 0.2-micron filter blocks sediment, asbestos fibers, and microplastics. More advanced filters certified to NSF/ANSI Standard 53 can reduce PFAS by over 99%. The key is matching the filter to the specific contaminant you’re concerned about, since no single filter removes everything. Check the certification label to see exactly which substances a given filter is tested against.