34.07° N · 118.10° W · WESTERN SGV
San Gabriel Valley water and what it does to fixtures
Much of the western SGV drinks groundwater from local wells, and groundwater carries minerals. How much depends on your supplier.
Groundwater and hardness
San Gabriel County Water District, for example, says its water comes from wells in the Main San Gabriel and Raymond groundwater basins (2025 report). The USGS explains that hardness comes mostly from dissolved calcium and magnesium.
The USGS scale: 0 to 60 mg/L soft, 61 to 120 moderately hard, 121 to 180 hard, and above 180 very hard.
Find your own number
- Look at your water bill for the supplier name.
- Search that supplier's annual water quality report, often called a Consumer Confidence Report.
- Find the line for total hardness, in ppm or mg/L (the same thing for water).
In San Gabriel, the city notes there are five water companies (city FAQ), so neighbors can have different numbers.
What scale does
Minerals come out of the water where it sits, dries or heats. Aerator screens clog, cartridges stiffen, fill valves stick, shower nozzles block, and tub spout diverters stop sealing.
Regular soaking of aerators and shower heads slows the buildup. Parts that already grind or leak usually need replacing, which is a straightforward fix.
Leaks waste water too
EPA WaterSense says the average household's leaks can waste nearly 10,000 gallons a year (EPA). In hard-water homes, many of those leaks start at scaled-up parts.