Compton Water Hardness & Quality Report (2026)

The City of Compton Municipal Utilities Department supplies water to approximately 95,000 residents across 10 square miles in southern Los Angeles County, California. Supply is mixed, drawn primarily from local groundwater wells tapping the Silverado, Lynwood, and San Pedro aquifers in the Los Angeles Forebay, supplemented by imported surface water from the Metropolitan Water District of Southern California (MWD), sourced from the Colorado River Aqueduct and State Water Project (via the California Aqueduct from Oroville Reservoir). Blending and disinfection occur at the Compton Water Treatment Plant.

The Los Angeles River coastal plain watershed recharges the aquifer system via the San Gabriel River spreading grounds. Aquifers consist of Quaternary alluvium and semi-consolidated formations including the Fernando Formation (Pliocene–Miocene marine shales and sandstones interbedded with volcanics). Limestone, dolomite, and evaporitic sediments from the uplifted Transverse Ranges contribute dissolved minerals, imparting a hard character to the groundwater. Imported MWD supplies from Sierra Nevada granitics and desert limestones blend with local groundwater, maintaining a moderately mineralized to hard overall chemistry.

Very hard water promotes significant limescale buildup in pipes, water heaters, dishwashers, and washing machines, reducing efficiency and raising energy costs by up to 30%. Dry skin, soap scum, and spotting on glassware are common. A water softener for whole-house treatment is strongly recommended; scale inhibitors or frequent descaling help untreated systems. pH typically runs 7.5–8.5. The supply meets lead and copper action levels per the 2021 Liberty Utilities CCR. Six contaminants — including arsenic and hexavalent chromium — exceed health guidelines per third-party analysis. Treatment includes chlorination, fluoridation (0.7 ppm), and blending; turbidity is controlled below 1 NTU.