Safe Levels of Lead in Water (ppm vs ppb): What the Numbers Mean

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People searching for safe levels of lead in water ppm usually have a number in front of them: a lab report, a utility notice or a result from a test kit, written in parts per million or parts per billion. The short answer is uncomfortable but clear. EPA has set its health-based goal for lead in drinking water at zero, and both EPA and CDC say no safe level of lead exposure has been identified for children. The numbers that appear in regulations, such as 15 parts per billion, are action triggers for water systems, not lines below which lead becomes harmless. This guide explains the difference between the health goal and the regulatory action level, converts the figures between ppb and ppm, walks through where lead comes from in a home, and covers testing, filtration, flushing and private wells. It summarizes EPA and CDC information current as of 2026 for general education. Health questions belong with a healthcare provider, and water-system questions with the local utility.

Part of our Lead Paint & Lead Testing guide — start there for the full picture →

Is There a Safe Level of Lead in Water?

Under the Safe Drinking Water Act, EPA sets non-enforceable health goals called maximum contaminant level goals, or MCLGs. EPA’s Basic Information about Lead in Drinking Water page states that the MCLG for lead is zero, because lead is a toxic metal that can be harmful to human health even at low exposure levels. The same page explains that lead is persistent and can accumulate in the body over time.

EPA also notes that EPA and CDC agree there is no known safe level of lead in a child’s blood. CDC’s page on lead in drinking water repeats the point that no safe blood lead level has been identified for young children and that all sources of lead exposure for children should be controlled. Young children, infants and fetuses are described by EPA as particularly vulnerable because effects occur at lower exposure levels than in adults.

So when a reading comes back as “low,” the accurate interpretation is “lower,” not “safe.” Any lead detected is a reason to look for the source and reduce exposure, with the urgency depending on the level, who drinks the water and how easy the fix is. Water is also only one route. EPA estimates drinking water can make up 20 percent or more of a person’s total lead exposure, and that infants who consume mostly mixed formula can receive 40 to 60 percent of their exposure from water. For the bigger picture on lead in the home, including paint and dust, see the asbestos and lead guide and the lead hub.

Understanding the Units: ppm vs ppb

Lead results are reported in several interchangeable units, and the mix-up between them causes a lot of confusion.

• ppm (parts per million) is the same as milligrams per liter (mg/L).
• ppb (parts per billion) is the same as micrograms per liter (µg/L).
• 1 ppm = 1,000 ppb. To convert ppb to ppm, divide by 1,000. To convert ppm to ppb, multiply by 1,000.

That makes the familiar regulatory figures look very small in ppm. The long-standing action level of 15 ppb is 0.015 ppm, or 0.015 mg/L. EPA’s LCRI questions and answers page refers to the current action level exceedance threshold in exactly those terms, at 0.015 mg/L. The newer 10 ppb level discussed below is 0.010 ppm.

Because lead matters at such low concentrations, most labs report it in ppb or µg/L. A result of “0.005 mg/L” and “5 µg/L” are the same reading. When comparing a home result to a utility report or to regulatory figures, convert everything to one unit first. Lab reports also list a reporting or detection limit, the lowest concentration the method can reliably measure. A result shown as “less than” that limit means lead was not detected at or above that level, not that the water contains none at all.

Lead Readings in ppb and ppm: What They Mean

The table below converts common readings and offers a hedged, general interpretation. It is not medical advice and does not replace guidance from a local health department or utility.

A single home result is not the same as a system-wide compliance test. Regulatory action levels are applied to a set of tap samples across a water system, not to an individual faucet. That distinction is explained in the next section.

The Action Level: 15 ppb Now, 10 ppb Under the LCRI

For most contaminants EPA sets an enforceable maximum contaminant level. For lead, EPA’s basics page explains that it instead set a treatment technique, because lead in drinking water often results from corrosion of plumbing owned by water system customers. That treatment technique is the Lead and Copper Rule (LCR). It requires water systems to control the corrosivity of their water and to collect tap samples from homes more likely to have lead plumbing.

Under the LCR, if more than 10 percent of a system’s tap samples exceed the lead action level of 15 parts per billion, the system must take additional steps, which EPA lists as further optimizing corrosion control for certain systems, educating the public and replacing the portions of lead service lines under the system’s control. EPA notes the rule was issued in 1991 and revised in 2000, 2007, 2021 and 2024.

The 2024 revision is the Lead and Copper Rule Improvements (LCRI). EPA’s LCRI page describes a final rule requiring water systems to identify and replace lead pipes within 10 years, more rigorous testing and “a lower threshold requiring communities to take action.” EPA’s LCRI questions and answers page states that the rule lowers the lead action level to 10 µg/L, which is 10 ppb or 0.010 ppm, to require more systems to act sooner on corrosion control and public education.

Timing deserves a hedge. EPA’s Q&A says water systems generally must begin complying with LCRI provisions three years after the final rule was published, with that date expected to be late 2027, and that systems continue to follow the existing rule until then, apart from certain earlier requirements already in effect. Regulatory timelines can shift through later rulemaking or litigation, so the current status for a specific system is best confirmed with the utility or the state drinking water program.

The key point for households: neither 15 ppb nor 10 ppb is a health-based “safe” line. They are triggers that tell water systems when broader action is required.

Where Lead in Tap Water Comes From

Lead rarely comes from the source water itself. It usually enters water on the way to the tap. EPA explains that lead gets into drinking water when plumbing materials that contain lead corrode, especially where water has high acidity or low mineral content. EPA and CDC both list lead pipes, faucets and fixtures as the most common sources.

• Lead service lines. The pipe connecting a home to the water main. EPA says that where these exist, they are typically the most significant source of lead in water, and that lead pipes are more likely in older cities and homes built before 1986.
• Lead solder. Used to join copper pipes in many older homes. CDC notes that plumbing fixtures, solder and pipe fittings made before 1986 may contain lead.
• Brass and chrome-plated brass fixtures. EPA identifies these as the most common problem in homes without lead service lines.
• Galvanized iron pipes. CDC lists these among materials that may contribute lead in homes without a lead service line.

How much lead reaches the glass depends on water chemistry, temperature, how long water sits in the pipes, the amount of wear and whether protective scale has formed. That is why first-draw samples taken after water sits overnight often read higher than samples taken after the tap has run. For more on the mechanics, see the guide to lead pipe corrosion. Treatment equipment can play a role as well; the guide on water softeners covers how softened water interacts with household plumbing.

Federal law has also tightened what counts as “lead-free” plumbing. EPA’s basics page explains that changes to the Safe Drinking Water Act reduced the maximum allowable lead content to a weighted average of 0.25 percent across wetted surfaces of pipes, fittings and fixtures, and 0.2 percent for solder and flux. Newer fixtures therefore contribute far less lead than older ones, though replacing a fixture does not address a lead service line.

How to Test Tap Water for Lead

EPA states plainly that lead cannot be seen, tasted or smelled in water, so testing is the only sure way to know. The agency notes that testing costs typically run between $20 and $100 and that a list of certified laboratories is available from state or local drinking water authorities.

Good starting points:

• Ask the utility first. CDC calls the local water authority the first source for testing and identifying lead contamination. Many systems test on request, and the annual Consumer Confidence Report summarizes system-wide results.
• Use a certified lab. Home screening kits vary in sensitivity. A certified laboratory using a proper sampling protocol gives a more defensible number.
• Follow sampling instructions exactly. First-draw, sequential and flushed samples answer different questions. Sequential sampling can help separate fixture lead from service line lead.
• Retest after changes. CDC notes that risk can rise during and for up to six months after water main or service line work, so retesting after construction nearby makes sense.

The guide to lead in water tests compares kit and lab options, and the overview of lead in water testing services explains what professional sampling includes. For general background on the topic, see lead in water.

Reducing Lead: Filters, Flushing and Cold Water

EPA lists several steps households can take, separately or in combination, when concerned about lead in water. The list is not ranked, and EPA notes not all actions reduce lead equally.

Use a filter certified for lead. EPA advises using a filter certified to remove lead and following the manufacturer’s instructions on installation and cartridge replacement, since expired cartridges can be less effective. CDC says certification should indicate NSF/ANSI Standard 53 for lead removal and NSF/ANSI Standard 42 for particulate removal. Filter packaging and certification listings should be checked for the specific lead claim, since not every filter certified under a standard is certified for lead. See the guide on lead in water filters for how to compare options.

Flush stagnant water. EPA explains that the longer water sits in pipes, the more lead it may contain, and suggests running water before drinking, for example by running the tap, showering or running a load of laundry or dishes. Flushing time depends on whether the home has a lead service line and how long it is, so EPA recommends asking the utility about flushing times locally.

Use cold water only. Both EPA and CDC advise using cold water for drinking, cooking and preparing baby formula, because warm or hot tap water can carry more lead.

Do not rely on boiling. EPA and CDC both state that boiling does not remove lead.

Clean aerators. EPA recommends regularly cleaning faucet screens, where lead particles can collect.

Know the service line. Ask the utility what the service line is made of; if records are missing, a licensed plumber may be able to help, according to EPA.

On showering: EPA says bathing and showering should be safe even if water contains lead over the action level, because human skin does not absorb lead in water, with the caveat that individual circumstances can vary.

Private Wells and Lead

Homes on private wells fall outside the Lead and Copper Rule, which applies to public water systems. Well owners are responsible for their own testing. EPA suggests that well users check with the health department or nearby utilities that use groundwater for information on local contaminants of concern.

Lead in well water usually comes from the same places as in city homes: older pumps, brass fittings, solder and household plumbing, along with water chemistry that encourages corrosion. Testing for lead alongside a broader panel is a sensible step when buying a home on a well or after replacing pump components. The guide to well water testing covers what to test for and how often.

Reading a Utility Report Against a Home Result

EPA requires community water systems to deliver an annual water quality report, the Consumer Confidence Report, to customers by July 1 each year. These reports often show a lead figure described as a “90th percentile” value along with the number of sampled sites above the action level. That statistic is designed for compliance: it describes the system’s sampled homes as a group, not any one address.

A few points make the comparison easier:

• Check the units. Utility reports may use ppb, µg/L or mg/L. Convert to one unit before comparing.
• Look at the sample count. A system-wide figure based on homes with known lead plumbing tells a different story than one based on newer neighborhoods.
• Remember that a good system figure does not clear a house. Lead often comes from plumbing on the customer’s side, so a home with old solder or fixtures can read higher than the system average.
• Note whether the sample was first-draw. A home result taken after flushing is likely to read lower than a first-draw sample from the same faucet.
• Watch for notices. EPA’s Public Notification Rule requires public water systems to alert customers if there is a problem with their drinking water, including notifications tied to lead action level exceedances.

CDC also cautions that water sampling results can vary with the time of day, season, sampling method, water flow and other factors. One reading is a snapshot. Two or three samples taken under consistent conditions give a much better picture of what is actually coming out of the tap day to day.

Who Should Be Most Cautious

Every household benefits from lower lead, but some situations call for extra care with any detectable reading.

Infants on formula. CDC notes that infants who drink formula prepared with lead-contaminated tap water may be at higher risk because of the large volume they consume relative to body size. Using filtered or certified bottled water for formula is a common precaution while a source is being investigated.

Pregnancy. EPA explains that lead stored in bones can be released during pregnancy and can cross the placenta, with possible effects including reduced fetal growth and premature birth.

Young children. EPA lists behavior and learning problems, lower IQ and hyperactivity, slowed growth, hearing problems and anemia among the effects of low blood lead levels in children.

For anyone in these groups, a blood lead test through a healthcare provider is the way to measure actual exposure. CDC recommends that public health actions begin at a blood lead level of 3.5 micrograms per deciliter, as noted on EPA’s basics page. A water result shows one possible source; a blood test shows what the body has absorbed from all of them combined, including paint, dust and soil.

Colorado Notes

Many Front Range utilities have been building lead service line inventories and replacement programs in response to federal requirements, and some offer free or discounted testing, filters or service line replacement for eligible homes. Program details, eligibility and timelines differ from utility to utility and change over time, so the most reliable step is to contact the water provider directly and ask what records it has for a specific address. Homes built before 1986 in older neighborhoods are the most likely to have lead solder or older fixtures, even where the service line itself has been replaced.

Lead in water and lead in paint often turn up in the same older homes. If the house predates 1978, the guide on when lead paint was stopped explains why paint and dust deserve a look as well.

References

• U.S. EPA: Basic Information about Lead in Drinking Water
• U.S. EPA: Lead and Copper Rule Improvements
• U.S. EPA: LCRI Questions and Answers
• CDC: About Lead in Drinking Water

Holding a lead result and unsure what it means for the house? Send us the number, the units on the report and the age of the home, and we can help point out sensible next steps.