U.S. Tap Water Safety Guide

1. How the EPA Regulates Your Drinking Water

Most Americans get their water from a public water system — a utility that draws from a lake, river, or underground aquifer, then treats it and pipes it to homes and businesses. The U.S. Environmental Protection Agency (EPA) regulates these systems under the Safe Drinking Water Act (SDWA), which has been federal law since 1974.

Under the SDWA, the EPA sets legal limits — called Maximum Contaminant Levels (MCLs) — for over 90 contaminants. Every public water system serving at least 25 people must test for these contaminants on a regular schedule and report the results to the EPA. If a system exceeds an MCL, that's a health-based violation — and they're legally required to notify customers.

Here's something important that most people don't realize: the EPA actually sets two numbers for each contaminant. The first is the Maximum Contaminant Level Goal (MCLG) — the level at which there is truly no known health risk. For carcinogens like lead, benzene, and arsenic, the MCLG is zero. The second is the actual enforceable MCL, which is set as close to the MCLG as "feasible" given available treatment technology and cost.

This distinction matters. A water system that's technically "in compliance" — no MCL violations — can still have detectable levels of contaminants that health experts consider problematic. That's why WaterSafeCheck looks at multiple factors, not just whether a system has had violations.

2. Understanding Water Quality Grades (A–F)

WaterSafeCheck assigns each ZIP code a letter grade from A to F based on a composite safety score (0–100). The grade is a quick summary — but it's always worth clicking through to see the specific factors behind it.

3. Lead in Tap Water: The Full Picture

Of all the contaminants I've tracked over the years, lead is the one that worries me most — not because it's the most common, but because of what it does at very low levels and how easy it is to miss.

Unlike most contaminants, lead in drinking water usually doesn't come from the source — it comes from your own home's plumbing. Lead service lines (the pipes that connect the main water line to your house), lead solder used to join copper pipes, and older brass fixtures can all leach lead into water, especially when the water sits in the pipes for several hours.

Five Things You Can Do Right Now

1. 1

   Flush your tap in the morning

   Run cold water for 30–60 seconds before using it for drinking or cooking — especially after it's been sitting overnight. This flushes lead-contaminated water that sat in your pipes out of the system.

2. 2

   Use cold water only for drinking and cooking

   Hot water dissolves lead from pipes much faster than cold. Never use hot tap water to make formula, cook pasta, or fill a kettle for drinking.

3. 3

   Get a certified filter

   NSF/ANSI Standard 53 certified filters are independently tested to remove lead. Look for the NSF mark on the packaging — don't trust marketing claims alone. Reverse osmosis systems (NSF/ANSI 58) also remove lead.

4. 4

   Test your specific tap

   Utility-wide lead data doesn't tell you what's coming out of your faucet. Your own plumbing matters more. Many state health departments offer free or low-cost lead testing kits. It's the only way to know for sure.

5. 5

   Check if your home has lead service lines

   Homes built before 1986 are most at risk. Contact your water utility — they are now required to identify and inventory lead service lines. If you have one, ask about replacement programs; many utilities offer them for free.

4. PFAS "Forever Chemicals" — The New Concern

PFAS (per- and polyfluoroalkyl substances) are a group of over 12,000 synthetic chemicals that have been used in manufacturing since the 1940s. They're in nonstick cookware, water-resistant clothing, food packaging, stain-resistant carpet treatments, and — crucially for water quality — in the firefighting foam used at airports and military bases for decades.

They're called "forever chemicals" because the carbon-fluorine bond they're built on is one of the strongest in all of chemistry. These compounds don't break down in the environment, and they accumulate in the human body over time — a process called bioaccumulation.

Standard water filters — including most pitcher-style filters like Brita — do not reliably remove PFAS. The technologies that work are granular activated carbon (GAC), reverse osmosis, and high-pressure membrane filtration (nanofiltration). Look for filters specifically certified by NSF International for PFAS removal.

5. Disinfection Byproducts: THMs and HAA5s

Here's the water quality paradox that most people don't know about: the chlorine utilities add to kill dangerous bacteria can itself create new contaminants. When chlorine reacts with naturally occurring organic matter in source water — decaying leaves, algae, soil runoff — it forms compounds called disinfection byproducts (DBPs).

The two groups regulated by the EPA are Total Trihalomethanes (TTHMs) and Haloacetic Acids (HAA5s). These are most common in surface water systems that treat water from rivers and lakes, where there's more organic material to react with. DBP violations are among the most common health-based violations in the EPA database — which is one reason they show up so often in C and D-graded systems.

Practical tip: Letting tap water sit uncovered in a pitcher or open container for 30–60 minutes allows some volatile THMs to evaporate. This helps with taste and reduces some exposure — but it doesn't remove HAA5s or most other contaminants. A carbon block filter certified to NSF/ANSI 42 or 53 is more reliable.

6. How to Read Your Consumer Confidence Report

Every public water utility in the United States is required by law to send customers an annual Consumer Confidence Report (CCR) — sometimes called a Water Quality Report or Annual Drinking Water Quality Report — by July 1 each year. If you're a renter, your landlord is required to give it to you.

The CCR is the most detailed source of water quality information available for your specific water system. It contains measured contaminant levels, not just whether violations occurred. Here's what to look for when you receive one:

7. EPA Contaminant Limits — Reference Table

Key regulated contaminants, their EPA MCLs, public health goals, health effects, and common sources. This covers the contaminants most commonly found in violation records. The EPA regulates over 90 contaminants in total.

Source: EPA National Primary Drinking Water Regulations. MCLs in mg/L unless noted. See epa.gov for the complete list of 90+ regulated contaminants.

8. Water Filters: What Actually Works

The most important thing I can tell you about water filters: the marketing is often misleading. A filter that "improves taste" is not the same as one that removes lead. The only way to know if a filter does what it claims is to look for certification from NSF International or the Water Quality Association (WQA) — independent organizations that actually test filters in labs.

9. Infants, Pregnant Women & Vulnerable Populations

The same water that's safe for a healthy adult can pose real risks for certain populations. When I worked in compliance, the questions that kept me up at night were never about the average healthy adult — they were about the families who had no idea their water system had a lead problem.

10. When to Call the EPA or Your State

Most water quality issues are handled by your local utility without any need to escalate. But there are situations where you should go directly to regulators.

11. Frequently Asked Questions