Southern California · lead guide

Lead in Southern California tap water.

FilteredWTR pulled the most recent Lead and Copper Rule result for 292 public water systems in 7 Southern California counties from EPA records. 206 of them reported zero lead at the 90th percentile. One system reached the federal action level of 0.015 mg/L. The table below lists every system with a FilteredWTR city report, highest result first.

How the lead number works

Every water system covered by the Lead and Copper Rule collects samples from drinking water taps inside homes it serves, with priority given to homes whose plumbing is most likely to contain lead. The results get ranked from lowest to highest. The figure the system reports is the 90th percentile, the level that nine out of ten sampled homes came in at or under.

The federal action level is 0.015 mg/L, the same as 15 parts per billion. When more than 10 percent of sampled taps go over it, the 90th-percentile figure crosses that line and the system has to take steps that include adjusting its corrosion control treatment and notifying customers.

The action level is a trigger for treatment work. The CDC has not identified any safe blood lead level in children, and it links even low exposures to learning and developmental problems.

Where lead gets into the water

Lead rarely comes from the water source itself. It dissolves out of plumbing on the way to the faucet, most often from lead solder on older copper joints and from brass parts inside faucets and valves. Water that sits still in the pipes overnight picks up more of it.

A 90th-percentile figure describes a sample of homes spread across a whole service area. Your house can run higher or lower than the system number depending on its age and what its pipes are made of. In an older home, or one with young children, a test at your own tap is worth doing.

If lead turns up, a filter certified to NSF/ANSI Standard 53 for lead removes it at the kitchen tap. Check that lead appears on the product's certificate before you buy.

Latest lead results by water system

Of the 292 systems with a result on file, 206 reported no detectable lead, which the EPA records as 0 mg/L. Nine measured at or above 0.0075 mg/L, which is half the action level and the range FilteredWTR city reports mark as Caution. One system reached the action level itself. USMC - 29 Palms in San Bernardino County measured 0.02 mg/L for the period ending Dec 2024. It has no FilteredWTR city report, so the table below leaves it out. The highest result in the table is 0.0096 mg/L from Joshua Basin Water District, which serves Joshua Tree.

The date column shows when the EPA monitoring period for each result closes. Some of those periods are still open, so a few dates fall after Oct 2026. Systems without a FilteredWTR city report count toward the totals above and stay out of the table.

Sources: U.S. Environmental Protection Agency, Lead and Copper Rule · Centers for Disease Control and Prevention, Childhood Lead Poisoning Prevention · NSF International / American National Standards Institute, NSF/ANSI Drinking Water Treatment Standards · U.S. EPA, Safe Drinking Water Information System. System results as of Oct 2026.

Related guides: Hard water in Orange County · Water systems with EPA violations · Chlorine byproducts in Orange County · All city water reports