Lead in Water: Action Level vs. MCL (and Why Lead Has No MCL)
Lead is the one major drinking-water contaminant with no Maximum Contaminant Level. Here's why, what the 15 ppb action level actually means, and what changes in 2027.
TapGraded Editorial · Editorial team · July 13, 2026
Most drinking-water contaminants have a Maximum Contaminant Level (MCL) — a single enforceable number a system either meets or violates. Lead doesn’t. That surprises people, and it changes how you should read a lead result. The reason comes down to where lead comes from and how the rule is built.
Why lead has no MCL
The EPA sets a health goal for every contaminant, the MCLG (Maximum Contaminant Level Goal). For lead, the MCLG is zero — there is no known safe level of lead exposure. You can’t set an enforceable MCL of zero and hold a utility to it, because lead usually isn’t in the water when it leaves the treatment plant. It’s picked up on the way to your tap, from lead service lines, brass fixtures, and lead solder in household plumbing. So instead of an MCL, lead is regulated with a treatment technique under the Lead and Copper Rule.
What the action level actually means
Under the Lead and Copper Rule, systems sample high-risk taps and calculate the 90th-percentile result — the level 90% of samples fall below. If that value exceeds the action level of 15 ppb, the system must take steps: optimize corrosion control, expand public education, and in many cases replace lead service lines.
Here’s the part that matters for you: the action level is not a health-based “safe” line. It’s a threshold that triggers system-wide action. Because lead comes from your own plumbing, your tap can be above 15 ppb even when the system as a whole is below it — or vice versa. That’s why the Tap Grade treats a system’s lead 90th-percentile result as one signal among several, and why a certified tap test is the only way to know your own number.
What changes in 2027
The EPA’s Lead and Copper Rule Improvements (LCRI), finalized in 2024, lower the action level to 10 ppb (0.010 mg/L). Water systems are required to comply with the new requirements starting November 1, 2027. The rule also pushes systems toward replacing lead service lines and strengthens tap-sampling and public-education requirements.
What to do
- Look up your system’s lead 90th-percentile figure on its lead contaminant page and in its annual Consumer Confidence Report.
- If you have a home built before 1986 or a known lead service line, test your own tap — the utility’s number can’t stand in for it.
- If lead is confirmed, only specific filters are certified to remove it; see our lead filter guide.
Sources
- US EPA — “Lead and Copper Rule” — https://www.epa.gov/dwreginfo/lead-and-copper-rule
- US EPA — “National Primary Drinking Water Regulations” — https://www.epa.gov/ground-water-and-drinking-water/national-primary-drinking-water-regulations
- US EPA — “Lead and Copper Rule Improvements (LCRI)” — https://www.epa.gov/ground-water-and-drinking-water/lead-and-copper-rule-improvements
Source: Regulatory facts cited inline against EPA sources; see Methodology & Data sources · Data as of July 13, 2026
This article is informational and is not health, legal, or engineering advice. Questions or corrections: contact@tapgraded.com.