Tustin Water Hardness & Quality Report (2026)

The City of Tustin Water Services provides drinking water to approximately 66,000 residents across Tustin and parts of adjacent areas in Orange County, California. Primary sources are groundwater from the Orange County Groundwater Basin, including the Talbert and Foreman aquifers. Water is treated at local utility-managed facilities, with blending from imported surface water supplies during peak demand or basin recovery projects. The system meets all EPA standards and holds an A-grade quality rating.

The supply originates from the Orange County Groundwater Basin watershed, encompassing recharge from the Santa Ana River and local precipitation infiltrating through spreading grounds. Key geological features include Quaternary alluvial aquifers formed from riverine sediments overlying older Pleistocene Coyote Hills Formation clays and sands. The basin's geology — dominated by carbonate-rich sediments eroded from the Peninsular Ranges and Santa Ana Mountains — imparts a hard character to the groundwater through natural mineral leaching, contributing to elevated dissolved solids typical of regional supplies.

At this hard level, residents experience significant scale buildup in pipes, water heaters, dishwashers, and washing machines, reducing efficiency and lifespan while increasing energy costs. Soap lathering is reduced, leading to dry skin and hair. Regular descaling of fixtures and appliances is recommended, and a water softener is advisable to mitigate these effects and extend equipment life. The utility reports excellent compliance with no EPA violations and all contaminants meeting MCLGs; treatment includes disinfection with chlorine (residual 0.9–2.3 ppm), filtration, and blending to ensure reliability.