Home Water Quality: What’s in Yours, and What to Do About It

The baseline. Start with the baseline, stated fairly. In 2023, about 96% of US public water systems recorded no violation of a federal health-based drinking water standard, according to EPA’s national compliance report; roughly 4% did. The same data shows about one in five systems had a monitoring or reporting violation, which doesn’t mean contamination but does mean the picture for those systems is less complete. So the baseline is reassuring, but not universal. Most public systems meet enforceable federal health standards. Your city and your home determine whether that general picture applies to you.

Legal vs. health — EPA’s two numbers. Next, separate two questions that get collapsed constantly. “Meets the legal limit” and “is best for health” are not the same thing, and EPA itself builds the difference into two numbers for most contaminants. The Maximum Contaminant Level (MCL) is the enforceable legal limit, set as close to the health goal as feasible after accounting for treatment technology and cost. The Maximum Contaminant Level Goal (MCLG) is the purely health-based target, set with a margin of safety and often at or near zero for substances linked to cancer. When those two numbers differ, the gap isn’t a loophole or an oversight. It’s the distance between the health target EPA would set on health alone and the limit it can actually enforce given today’s treatment technology and cost. That gap is where a lot of the confusion starts.

PFAS: a live example. PFAS, the “forever chemicals,” show how this works, and they’re a live case. In its 2024 rule, EPA set an enforceable limit of 4 parts per trillion for PFOA and for PFOS while setting the health goal for both at zero; the 4 ppt figure reflects what is currently measurable and feasible to regulate, not a level EPA calls risk-free. Worth noting: another federal science body, the ATSDR, sets health-based screening levels for these chemicals that work out higher than EPA’s 4 ppt limit, not lower, a useful reminder that “health-based” does not automatically mean “stricter.” As of June 2026, EPA has proposed to let eligible water systems request more time to meet the PFOA and PFOS limits, and to rescind limits for PFHxS, PFNA, HFPO-DA, and the Hazard Index mixture, but those changes are proposals, not final rules. EPA says the proposed rescission is based on a procedural flaw in how the 2024 rule was made, not on a reassessment of the underlying health-risk findings for those PFAS. Those 2024 limits still stand; only a final rule changes them, and the proposed deadline extension is a separate question from the limits themselves.

The order we weigh sources. That is the order we use. The EPA’s enforceable limit comes first, because it is the law. EPA’s health goal comes next, along with the World Health Organization’s guideline where the comparison is useful. On arsenic, for instance, the enforceable US limit and the WHO guideline land at the same number while EPA’s health goal is zero, which is mainly a feasibility difference, not a different view of the hazard. For certain contaminants, we also use ATSDR toxicology or CDC risk framing when those sources add something specific. For your own water, the most important document is local: your utility’s Consumer Confidence Report, which tells you what was measured where you live.

How we keep this honest. The goal is not to make tap water sound scarier than it is, or safer than it is. Alarmist filter marketing deserves skepticism, but so does the blanket claim that everything is perfectly fine. The test we use is simple: would both an EPA scientist and a mainstream toxicologist call this a fair representation of their position? If a sentence couldn’t pass that test, it doesn’t run. We use that same standard on the city guides and the deeper safety pages linked from this hub.