Lead is the most serious drinking-water contaminant in the US, and the most misunderstood in one specific way: the risk usually comes from the plumbing, not the water source. This page lays out the verified numbers on service lines, exceedances, health effects, and the crisis that changed the national conversation.
Lead service lines: the updated picture
The headline number has changed, and it’s worth getting right.
- Current estimate: roughly 4 million lead service lines remain in the US, per the EPA’s inventory-based update. That’s about 3 million confirmed lead or galvanized lines requiring replacement, plus about 1 million of unknown material that are likely to contain lead.
- Older projection: 9.2 million lead service lines, from the EPA’s 7th Drinking Water Infrastructure Needs Survey released in April 2023. This was a projection made before communities completed their mandated inventories.
The direction matters: once public water systems were required to actually inventory their lines, with a deadline of October 16, 2024, the confirmed count came in lower than the earlier projection, but still in the millions.
Lead pipes and solder were banned nationwide in 1986, though homes built before then, and some slightly later via lead solder and brass fixtures, remain the primary exposure sites.
Two things follow from the updated 4-million figure that aren’t obvious if you only remember the old 9.2 million. First, the revision was the result of the first-ever mandatory national inventory, meaning the lower number is both more accurate and a genuine improvement in national visibility into the problem. Second, “galvanized lines requiring replacement” are included because a galvanized line that was once downstream of a lead line can have absorbed lead into its interior scale and remain a source even after the lead line itself is removed. That nuance is why the count groups them together rather than counting bare lead pipe alone.
How many systems exceed lead limits
The EPA doesn’t publish a single clean annual headline count, but the scale is documented by independent analysis of federal data:
- Between January 2018 and December 2020, roughly 1,085 water systems had 90th-percentile lead samples exceeding 15 parts per billion, according to the Natural Resources Defense Council’s analysis.
- Approximately 12.9 million people, about 4% of the community-water-system population, received water from systems detecting lead at or above 15 ppb during 2021–2024, per the same NRDC report.
- The EPA action level was 15 ppb, and under the 2024 Lead and Copper Rule Improvements it is set to lower to 10 ppb, effective around 2027, per the EPA.
The key distinction is that the action level is a regulatory trigger. If more than 10% of sampled taps exceed it, the system must act. It is not a safety threshold, because there is no safe level of lead.
It’s also worth noting the sampling caveat, because it’s the single biggest reason lead exceedances get under-reported. Lead testing samples a subset of taps, and a system can be “in compliance” while specific homes — especially older ones with lead service lines — have elevated lead. The action level is designed to catch system-wide corrosion problems, not to certify that every individual tap is lead-free. That’s why household-level awareness matters even when your utility reports no exceedance.
Health effects: why there’s no safe level
The CDC is unambiguous: there is no identified safe blood lead level in children.
- The CDC’s Blood Lead Reference Value, the level used to identify children who need follow-up, is 3.5 micrograms per deciliter (µg/dL), updated down from 5.0 µg/dL in October 2021, per the CDC. It is a screening benchmark, not a toxicity threshold.
- Roughly 2.5% of US children ages 1–5 have blood lead levels at or above that reference value.
- Lead harms the developing brain and nervous system, with effects including reduced IQ, attention and behavior problems, and impaired growth that are largely irreversible.
Infants are at highest risk, both because they absorb lead more readily and because formula mixed with water is often their entire diet.
The screening threshold is worth understanding precisely, because it’s often misread. The 3.5 µg/dL figure is not a “safe” ceiling but a population-based reference point: the level at the 97.5th percentile of US children’s blood lead levels. Children above it are flagged for follow-up and intervention, but the harm from lead begins at levels far below it. This is the core reason the CDC, EPA, and pediatric authorities all emphasize that the only meaningful goal is to minimize exposure, not to get “under” some specific number.
The irreversibility is the other thing that separates lead from most drinking-water contaminants. Many water-quality issues — taste, hardness, even some microbial risks — are either transient or reversible. Lead’s effect on a developing brain is not: the IQ and behavioral effects documented in the epidemiological literature persist even after exposure ends, which is why the public-health emphasis lands so heavily on prevention rather than on treating elevated levels after the fact. For a parent, that framing translates to a simple rule: the time to act on lead is before a child ever shows a problem, because there’s no reliable way to undo the effect afterward.
Flint, Michigan: the crisis that exposed the plumbing
Flint is the case study in how source-water changes can turn old plumbing into a public-health emergency.
- In April 2014, Flint switched its water source from Detroit water to the Flint River without adding the required corrosion-control treatment. The more corrosive river water stripped protective scale from the city’s aging pipes.
- The result was widespread lead contamination affecting Flint’s roughly 99,000 residents, along with a Legionnaires’ disease outbreak, documented by the CDC’s Flint Lead Exposure Registry. It took years and a federal and state emergency response to address.
Flint’s lesson isn’t unique to Flint. It demonstrated that lead risk is a function of corrosion: when water chemistry changes, lead that was safely locked in pipe scale can leach into the supply.
The specific failure in Flint was the absence of a corrosion-control chemical called orthophosphate. Detroit’s water had included it, which built up a protective phosphate scale on the inside of the city’s pipes that kept lead from leaching. When Flint switched to the untreated Flint River water, that protective layer dissolved, and the lead underneath came into contact with the water supply. The technical detail matters because it reframes the risk: lead in pipes is dangerous primarily when water chemistry changes, not in steady state. That’s why a utility’s corrosion-control program — not the presence or absence of lead pipes alone — is the operative safety factor, and it’s exactly the thing regulators now require systems to demonstrate.
What this means for you
The practical, data-backed takeaways:
- Old home, test your plumbing risk. If your home was built before 1986, lead service lines or solder are a real possibility.
- Flush and use cold water. Water that has sat in pipes overnight has the highest lead concentration, and running the cold tap until it turns cold flushes it out. Hot water dissolves more lead, so never cook with it.
- No “safe amount” for kids. If you have young children in an older home, a point-of-use filter certified for lead is a cheap, targeted safeguard.
Lead in drinking water is the rare contaminant where the fix is mostly household-level and inexpensive, but only if you know your home’s plumbing risk in the first place.
It’s also the one place where the national statistics genuinely understate a household’s personal risk. The 4 million lead service lines figure is a national count, but risk isn’t evenly distributed: it concentrates in specific older neighborhoods, in specific regions with older housing stock, and in homes built during specific decades. That’s why the title question — “is my water lead-free” — can’t be answered from national data at all. It’s answered by knowing what’s in your specific stretch of pipe, which is something only you can determine for your own home. The good news, per the data above, is that the testing and the fix are comparatively cheap relative to the harm they prevent.
It’s also the one place where the national statistics genuinely understate a household’s personal risk. The 4 million lead service lines figure is a national count, but risk isn’t evenly distributed: it concentrates in specific older neighborhoods, in specific regions with older housing stock, and in homes built during specific decades. That’s why the title question — “is my water lead-free” — can’t be answered from national data at all. It’s answered by knowing what’s in your specific stretch of pipe, which is something only you can determine for your own home. The good news, per the data above, is that the testing and the fix are comparatively cheap relative to the harm they prevent.