For most people on a public water system in the United States, tap water is safe to drink. Public utilities are required to treat water to meet over 90 federal safety standards, and the vast majority of systems pass these tests year-round. But “safe by federal standards” doesn’t mean your water is free of every concern. Aging pipes, emerging chemicals, and where you live all play a role in what actually comes out of your faucet.
What “Safe” Actually Means
The EPA sets legal limits, called Maximum Contaminant Levels, for dozens of substances in public drinking water. These limits are based on what’s considered protective of health over a lifetime of daily consumption. A few of the most important ones: arsenic is capped at 10 parts per billion, nitrate at 10 milligrams per liter, and no more than 5% of a utility’s monthly samples can test positive for coliform bacteria, a marker for disease-causing organisms.
Lead works differently. There’s no “safe” concentration, so instead of a fixed limit, the EPA uses an action level of 10 parts per billion measured at the tap. If more than 10% of sampled homes in a system exceed that level, the utility has to take corrective steps. This distinction matters because lead contamination often comes from your own plumbing, not the water treatment plant.
The Biggest Risk: Your Pipes
Water can leave a treatment facility perfectly clean and still pick up lead on the way to your glass. Lead service lines, the pipes connecting the water main under the street to your home, are the primary culprit. Homes built before 1986 may also have lead solder in their interior plumbing. When these pipes corrode, lead leaches directly into your drinking water.
In October 2024, the EPA finalized a rule requiring water systems nationwide to identify and replace lead service lines within 10 years. That’s a significant step, but it means millions of lead pipes will remain in the ground for years to come. If your home has a lead service line or older plumbing, running cold water for 30 seconds to two minutes before drinking (especially first thing in the morning) helps flush out water that’s been sitting in contact with lead. Never use hot tap water for cooking or drinking, since heat pulls more lead from pipes.
PFAS: The Newer Threat
PFAS are a large family of synthetic chemicals used in nonstick coatings, waterproof fabrics, and firefighting foam. They’ve earned the nickname “forever chemicals” because they don’t break down in the environment or in your body. Widespread contamination of drinking water sources has made them a major public health concern.
The EPA now sets enforceable limits for six individual PFAS compounds. The two most studied, PFOA and PFOS, are each capped at 4.0 parts per trillion, an extraordinarily low threshold that reflects how potent these chemicals are even in tiny amounts. Water systems have until 2029 to comply, so testing and treatment are still ramping up across the country. Your annual water quality report (more on that below) will eventually include PFAS results if your utility detects them.
Germs and Parasites
Bacterial and parasitic contamination is rare in treated municipal water, but not impossible. Treatment plants that draw from rivers, lakes, or reservoirs are required to remove at least 99% of Cryptosporidium, a parasite that causes severe gastrointestinal illness and resists standard chlorine disinfection. Filtration is the main defense. Legionella, the bacterium that causes Legionnaires’ disease, is more of a concern in building plumbing systems (especially large buildings with complex water infrastructure) than in the water supply itself.
If you ever receive a boil-water notice from your utility, take it seriously. These are issued when there’s a confirmed or suspected breach in treatment, such as a water main break or a disinfection failure. Bringing water to a rolling boil for one minute kills virtually all harmful organisms.
Microplastics in Tap Water
Tiny plastic particles are now found in tap water virtually everywhere researchers have looked. If that makes you consider switching to bottled water, it’s worth knowing that bottled water contains roughly three times as many nanoplastic particles as treated tap water, according to research from Ohio State University. The health effects of ingesting microplastics are still being studied, but from a microplastics standpoint, tap water is the better option.
How to Check Your Water Quality
Every public water system is legally required to send you an annual Consumer Confidence Report by July 1st. This report lists every contaminant detected in your water, how the levels compare to federal limits, and where your water comes from. If you haven’t seen yours, you can look it up on the EPA’s CCR search tool at sdwis.epa.gov/fylccr. Just select your state and browse for your water system by county.
Reading the report is straightforward. Look for any contaminant that approaches or exceeds its legal limit. Pay particular attention to lead and copper results, disinfection byproducts (formed when chlorine reacts with organic matter in the water), and any noted violations. A clean report from your utility is reassuring, but remember: it reflects water quality at the treatment plant and in the distribution system, not necessarily at your specific faucet. If your home has older plumbing, a home test is the only way to know what you’re actually drinking.
If You Have a Private Well
Private wells serve about 23 million households in the U.S., and they’re not covered by any federal drinking water regulation. You are entirely responsible for testing and treating your own water. The CDC recommends testing your well at least once a year for total coliform bacteria, nitrates, total dissolved solids, and pH. If you live in an agricultural area, near industrial sites, or in a region with naturally occurring arsenic, you should test for those specific contaminants too.
Don’t rely on mail-order test strips for anything beyond a rough screening. For accurate results, contact a state-certified drinking water laboratory. The EPA maintains a directory of certified labs organized by state at epa.gov/dwlabcert. These labs can test for a wide range of contaminants and provide results you can actually trust and act on.
Choosing a Water Filter
If your water report or home test reveals a problem, or you simply want an extra layer of protection, a filter can help. But not all filters remove the same things. The key is matching the filter’s certification to the contaminant you’re concerned about.
- NSF/ANSI 53 certifies filters for health-related contaminants including lead, Cryptosporidium, and volatile organic compounds. If lead is your concern, this is the standard to look for.
- NSF/ANSI 58 covers reverse osmosis systems, which are effective against a broad range of contaminants including PFAS, arsenic, and nitrate.
- NSF/ANSI 401 covers emerging compounds like prescription drugs, over-the-counter medications, herbicides, and pesticides that may be present at trace levels.
Check the packaging or the manufacturer’s website for these specific certifications. A filter labeled “improves taste” (certified only to NSF/ANSI 42) reduces chlorine and sediment but won’t protect you from lead or other health-related contaminants. Pitcher filters, faucet-mount filters, and under-sink systems are all available with the right certifications. Replace filter cartridges on schedule, since an expired filter can actually release trapped contaminants back into your water.
Arsenic and Nitrate: Regional Concerns
Some contaminants are tied to geography. Arsenic occurs naturally in groundwater in parts of the Southwest, Midwest, and New England. Long-term exposure, even at levels near the federal limit, has been linked to skin changes, nerve damage in the hands and feet, cardiovascular disease, type 2 diabetes, and increased risk of lung, bladder, and skin cancers. Skin effects, including unusual pigmentation and thickening on the palms and soles, are often the first visible sign and can develop after roughly five years of exposure.
Nitrate is the bigger concern in farming regions, where fertilizer and animal waste seep into groundwater. It’s particularly dangerous for infants under six months old, in whom it can interfere with the blood’s ability to carry oxygen. If you have a well in an agricultural area and there’s an infant in the household, annual nitrate testing is essential.