Walnut Park Water Hardness & Quality Report (2026)

Walnut Park, California, in Los Angeles County — an unincorporated Los Angeles County community adjacent to Maywood and Huntington Park in the south Los Angeles industrial corridor — receives its water from the Los Angeles Department of Water and Power (LADWP), drawing from the Colorado River Aqueduct and State Water Project (SWP) imports through the south Los Angeles distribution system.

The moderately hard 154.5 mg/L hardness and elevated TDS of 447.2 mg/L (TDS/hardness ratio ~2.9 — reflecting evaporitic mineral loading) reflect the south Los Angeles blended imported supply's Colorado River calcareous and evaporitic character. The LADWP imported supply blends Colorado River water (draining Permian Supai Formation evaporitic — gypsum and halite TDS contributor, Cretaceous Mancos Shale calcareous) with State Water Project water from the Sierra Nevada (Cretaceous granodiorite). The Colorado River evaporitic component produces the elevated TDS relative to hardness.

At 154.5 mg/L, Walnut Park's water is moderately hard — scale builds in kettles and appliances over months, dishwashers benefit from rinse aid, and faucet aerators need periodic cleaning. Quarterly descaling is appropriate. The PFAS level of 6.4 ppt warrants a certified drinking water filter — the Los Angeles County south industrial corridor and the Colorado River PFAS background contribute to Walnut Park's readings.