East San Gabriel Water Hardness & Quality Report (2026)

East San Gabriel, California, in Los Angeles County — an unincorporated Los Angeles County community adjacent to Rosemead and Temple City in the San Gabriel Valley of east Los Angeles — receives its water from the San Gabriel Basin Water Quality Authority and local utilities, drawing from the San Gabriel Valley Groundwater Basin and Metropolitan Water District (MWD) imports through the east Los Angeles distribution.

The moderately hard 152.5 mg/L hardness and TDS of 439.1 mg/L (elevated TDS relative to hardness — reflecting the Colorado River MWD import's high dissolved sulfate and chloride) reflect the east Los Angeles San Gabriel Valley supply's moderate character — harder than the LADWP Owens Valley communities (Sunland: 33.5 mg/L) but typical for the San Gabriel Valley MWD-blended zone (Arcadia: ~148 mg/L; Temple City: ~155 mg/L). The San Gabriel Valley Groundwater Basin integrates local Quaternary alluvial aquifer (calcareous — primary hardness contributor) and MWD Colorado River imports (evaporitic TDS — dominant elevated TDS contributor).

At 152.5 mg/L, East San Gabriel'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 6.3 ppt warrants a certified drinking water filter — the San Gabriel Valley Superfund sites (Los Angeles County — TCE and industrial legacy with associated PFAS), the San Gabriel Basin industrial PFAS legacy, and the Los Angeles metro industrial corridor contribute to East San Gabriel's readings.