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Lead in Drinking Water: A Scientist's Guide For Your Home
January 16, 2025
Eric Roy, PhD | Chief Scientist
I have spent much of my career working on lead in drinking water. My first water filter company, Hydroviv, launched in direct response to the Flint water crisis. In 2019, I testified before the U.S. House Committee on Science, Space, and Technology about the gaps in the water filtration technology pipeline. Since then, my teams have built and shipped hundreds of thousands of certified lead filters for homes across the country.
The biggest source of lead contamination in drinking water is the lead service line, the pipe that connects the water main in the street to your home. An estimated 9.2 million American homes still have one. Homes built before 1986 carry extra risk, because lead can also be in the solder that joins copper pipes and in brass fixtures and faucet parts. Even a home that looks modern can have lead-containing components behind the walls or inside older valves.
On this the science is clear: there is no safe level of lead exposure. The stakes are highest for children, because lead interferes with brain development during the years it matters most, and even low levels are tied to lower IQ, learning and attention problems, and behavioral issues. In adults, long-term exposure is linked to cardiovascular disease, high blood pressure, and kidney damage. Lead also stores in bone and can be released back into the blood during pregnancy, which puts a developing child at risk even from a mother's past exposure.
Most people assume their water is fine because their city reports that it meets federal rules. The reality is more complicated. Lead is regulated under the EPA's Lead and Copper Rule, and unlike most contaminants it has no Maximum Contaminant Level. Instead there is an Action Level of 15 parts per billion, and a system counts as compliant if 90 percent of its tested samples come in below that.
That 15 ppb number is not a health-based threshold. It was set to balance cost and feasibility, not because 15 ppb is safe. The American Academy of Pediatrics recommends that lead in drinking water stay below 1 ppb (the target it set for school drinking fountains), and toxicologists will tell you the only truly safe level is as close to zero as you can get. So a city can meet every federal rule while still delivering water to individual homes at levels well above what health experts consider acceptable. Legal and safe are not the same thing.
The only way to know a water filtration product protects against lead is to look for an NSF/ANSI Standard 53 certification claim for lead reduction. That certification requires independent lab testing that the filter reduces lead to very low levels, that it holds up across its entire rated service life, and that it performs under a wide range of conditions. NSF, WQA, and IAPMO can all issue this certification.
Install the filter where you actually drink and cook, whether that is an under-sink system, a countertop unit, or a dedicated filtered tap. And replace the cartridge on schedule: a certified filter is only certified for a defined service life, and its performance falls off quickly once it is spent.
Because lead contaminates water when it sits stagnant in the pipes, you can run your water for 2-3 minutes before using it for drinking or cooking. This ensures that you're drinking water that hasn't been sitting stagnant in the pipes.
How do I know if I have lead pipes? Try a scratch test on the pipe where it enters your home, usually in the basement. Lead is soft, scratches easily, and is shiny silver underneath. Copper is the color of a penny. Galvanized steel is hard, gray, and magnetic.
How do I know if my brass parts contain lead? It is not a perfect check, but brass plumbing parts like valves and shutoffs are usually stamped with an "LF" (lead free) mark or a check symbol.
Should I test my water? If you decide to test your water, make sure you perform what's called a "first draw" lead test. What you'll do is let your water sit stagnant/unused for at least 8 hours before pulling your sample. This allows water to sit in the pipes to simulate what happens when water goes unused overnight.