For most people in the United States, tap water is safe to drink. Public water systems are legally required to meet federal standards covering more than 90 contaminants, and the vast majority of systems pass every year. That said, safety isn’t universal. Where you live, the age of your plumbing, and whether you’re on a public system or a private well all affect what’s actually coming out of your faucet.
How Public Water Systems Are Regulated
The Safe Drinking Water Act requires the EPA to set legal limits on over 90 contaminants in drinking water, including bacteria, heavy metals, pesticides, and industrial chemicals. These limits are designed to reflect both what protects human health and what treatment plants can realistically achieve. Water systems must follow specific testing schedules and methods, and the results are public.
Individual states can set their own standards as long as they’re at least as strict as the federal ones. Some states, particularly California and New Jersey, enforce tighter limits on certain chemicals. Every year by July 1, your water supplier is required to send you a Consumer Confidence Report (also called an annual drinking water quality report) that tells you where your water comes from and exactly what’s in it. If you’ve never seen yours, the EPA maintains a searchable database at its website where you can look it up by state and county.
Lead: The Biggest Plumbing Risk
Lead doesn’t typically come from the water source itself. It leaches into water from old lead pipes, solder, and fixtures, particularly in homes built before 1986. That distinction matters because your water utility’s tests might look clean while the water at your tap tells a different story.
The health effects of lead are well established. In children, even low levels of exposure have been linked to learning disabilities, lower IQ, hyperactivity, slowed growth, hearing problems, and anemia. Young children, infants, and fetuses are especially vulnerable because lead causes harm at lower levels in developing bodies than in adults. During pregnancy, lead stored in a mother’s bones can be released and reach the fetus, increasing the risk of premature birth and reduced fetal growth.
Adults aren’t immune. Lead exposure raises blood pressure, increases the risk of hypertension, decreases kidney function, and can cause reproductive problems in both men and women. If your home has 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 pipes. You can also have your water tested through your local health department, often for free or at low cost.
PFAS: The Newest Regulated Threat
In 2024, the EPA established its first legally enforceable limits for six PFAS compounds, sometimes called “forever chemicals” because they don’t break down in the environment. These synthetic chemicals are linked to cancer, liver damage, immune system effects, and developmental problems. They entered water supplies through industrial discharge, firefighting foam, and consumer products.
The new limits are extremely tight. PFOA and PFOS, the two most studied PFAS chemicals, are now capped at 4 parts per trillion. Four other compounds (PFHxS, PFNA, and a chemical commonly known as GenX) are limited to 10 parts per trillion each. When two or more of these chemicals appear together, water systems must also meet a combined hazard index. Public water systems will need to test for these compounds and treat the water if levels exceed the new limits, though full compliance will take several years.
Germs That Can Survive Treatment
Chlorine disinfection kills most bacteria and viruses in public water, but a few organisms are harder to eliminate. Cryptosporidium and Giardia, both parasites that cause severe gastrointestinal illness, can resist standard chlorination. Most large water systems use additional treatment steps to handle them, but smaller systems and older infrastructure may be more vulnerable during heavy rainfall or equipment failures.
Some viruses also pose challenges. Norovirus is somewhat resistant to chlorine, and enteroviruses are not effectively killed by standard disinfectants. Both are too small to be removed by most conventional water filters. Boiling water for one minute (three minutes above 6,500 feet elevation) kills all of these organisms. Reverse osmosis, UV light, and ozone treatment are also effective against the parasites.
Private Wells Are a Different Situation
If you get your water from a private well, federal drinking water standards don’t apply to you. There’s no required testing, no mandated treatment, and no annual quality report. You’re responsible for everything.
The CDC recommends testing your well at least once a year for total coliform bacteria, nitrates, total dissolved solids, and pH. Depending on your region, you may also need to test for lead, arsenic, mercury, radium, pesticides, herbicides, and volatile organic compounds. Your local health or environmental department can tell you which contaminants are common in your area.
Arsenic is a particular concern for well owners in the Southwest, where about 16 percent of drinking water wells sampled by the U.S. Geological Survey exceeded the federal limit of 10 parts per billion. That rate is more than double the national average. Wells drawing from glacial aquifers in the northern U.S., crystalline rock aquifers along the Appalachian region, and alluvial aquifers in the Mississippi River Valley also show elevated arsenic. Long-term arsenic exposure increases the risk of cancer, heart disease, and diabetes.
What Your Water’s Color, Smell, or Taste Means
Not every change in your water signals a health risk, but some do. Here’s what common signs typically indicate:
- Brown, red, or orange water: Usually iron rust from aging pipes. Generally not dangerous but worth investigating if persistent.
- Green or blue water: Corrosion of copper plumbing. If you see blue-green stains on fixtures, copper and potentially lead may be leaching into your water. This can be a health concern.
- Milky or cloudy water: Almost always tiny air bubbles. Fill a glass and wait 30 seconds. If it clears from the bottom up, it’s just air.
- Chlorine smell or taste: Normal in treated water, though a very strong chemical taste may indicate high chlorine levels or interaction with organic buildup in your plumbing.
- Rotten egg smell: Hydrogen sulfide, either naturally occurring in the water or from bacteria growing in your drain or hot water heater. Unpleasant but not usually harmful.
- Gasoline, fuel, or solvent smell: Potentially serious. Stop using the water. This can indicate contamination from an underground storage tank leak.
- Salty taste: High naturally occurring sodium, magnesium, or potassium. In coastal areas, it may mean seawater is seeping into the supply.
Choosing the Right Water Filter
If you want extra protection or your water has a known issue, a filter can help, but only if it’s certified for the specific contaminant you’re concerned about. The certification standards that matter most are set by NSF International:
- NSF/ANSI 42: Reduces chlorine, taste, and odor. This is what most basic pitcher filters and faucet attachments are certified for. It improves how water tastes and smells but doesn’t remove health-related contaminants.
- NSF/ANSI 53: Reduces contaminants with known health effects, including lead, certain pesticides, and volatile organic compounds. If lead in old plumbing is your concern, this is the standard to look for.
- NSF/ANSI 401: Covers emerging contaminants like pharmaceuticals and chemicals not yet regulated by the EPA. These filters handle compounds that standard treatment plants weren’t originally designed to remove.
Reverse osmosis systems are the most thorough option for home use, effective against lead, arsenic, PFAS, nitrates, and most microorganisms. They’re more expensive and produce wastewater, but they address the broadest range of contaminants. Whatever filter you choose, check the product packaging or the manufacturer’s website for the specific NSF certification. A filter labeled “improves taste” won’t protect you from lead or PFAS.
How to Check Your Own Water
Start with your Consumer Confidence Report. It lists every contaminant your utility tested for, the levels detected, and whether those levels met federal limits. You can find it on your water utility’s website or search the EPA’s database by state and county. Pay attention to any contaminant listed as approaching or exceeding its legal limit, and note whether your system received any violations during the reporting year.
If your report looks clean but you have older plumbing, a home lead test is still worthwhile. Many local health departments offer free test kits. For well owners, annual lab testing is the only way to know what’s in your water, since conditions underground can change from year to year due to rainfall, agricultural activity, and shifting water tables. Labs certified by your state will run a basic panel for $20 to $150 depending on what you test for.