Updated November 1, 2026

Los Angeles tap water: one city, four sources, very different hardness

LADWP's tap water isn't one product. Snowmelt from the Eastern Sierra, Colorado River and Northern California water bought from Metropolitan, local wells and a small share of recycled water all feed the system, and their mineral content differs by more than double.

The 2025 supply mix

According to the 2025 report, published in 2026, the Los Angeles Aqueduct supplied 44% of the city's water. Imported water purchased from the Metropolitan Water District of Southern California made up 52%, drawn from the State Water Project and the Colorado River Aqueduct. Local groundwater added 1% and recycled water 3%. The aqueduct carries water from the Owens Valley and Mono Basin, which LADWP monitors because those watersheds are exposed to geothermal activity. Aqueduct water is treated at the Los Angeles Aqueduct Filtration Plant, where ultraviolet treatment guards against Cryptosporidium and Giardia. Neither was found in treated water in 2025.

Hardness by source (mg/L as CaCO3, 2025 averages)

That gap shows up in the kitchen. Customers on mostly aqueduct water see moderately hard water. Customers fed by MWD water from Weymouth or Diemer get water hard enough that softeners and descaling become a real cost question. Sodium follows the same pattern: about 39–40 mg/L in aqueduct and well water and about 88–89 mg/L from Weymouth and Diemer. You can ask LADWP which source serves your address, then run the number through our softener sizing calculator.

Arsenic: below the limit, but on the list

The highest arsenic level LADWP detected in 2025 was 7.0 µg/L. The federal and state limit is 10 µg/L. California requires utilities to explain any level above 5 µg/L, so the report includes a short notice. Its advice: use cold water for drinking, flush a tap that has been sitting for one to two minutes, and use a filter certified to NSF-53 if you want extra reduction.

A lead story that is mostly good news

LADWP says its service line inventory found no lead service lines, and it holds a non-lead designation from the State Water Board. As of December 2025 it had replaced more than 607,000 of its roughly 700,000 active meters with lead-free meters. At the tap, 3 of 105 sampled homes exceeded the 15 µg/L action level, and the 90th-percentile result was under 5 µg/L. When lead does appear here, it comes from inside the building: older brass fixtures and solder.

Reservoir roofs and the Griffith Park reading

The report discloses three issues. On May 31, 2023, the State Water Board flagged a significant deficiency at Solano Reservoir for small holes in its corrugated metal roof, and a corrective plan was filed. On October 17, 2025, a similar deficiency was found at Maclay Reservoir. Maclay was taken out of service on February 10, 2026 and drained for roof repairs, with completion expected in mid-2026. Separately, samples at Griffith Park in September 2023 showed total trihalomethanes as high as 136 ppb, above the 80 ppb limit, which is measured as a running annual average.

PFAS

LADWP reports more than a thousand PFAS samples from its system. PFAS were found in a few individual wells at the Pollock Well Field, but no compound covered by proposed or actual state or federal PFAS rules was detected in water entering distribution.