Northwood Water Hardness & Quality Report (2026)

Northwood, California, in Orange County — a master-planned neighborhood in the City of Irvine, developed as part of the Irvine Company's comprehensive Irvine Ranch planning effort along the inland San Joaquin Hills corridor — receives its municipal water from the Irvine Ranch Water District (IRWD), which draws from Metropolitan Water District of Southern California (MWD) imported supply and local Irvine Basin groundwater. IRWD is one of California's most innovative water districts, operating an extensive dual-distribution system for recycled and potable water.

The moderately hard 146 mg/L hardness and TDS of 412.6 mg/L reflect the IRWD supply's blended character — a mix of MWD imported water and Irvine Basin alluvial groundwater. MWD imported water blends the harder Colorado River Aqueduct supply (~300+ mg/L hardness at intake, softened in treatment) with the softer State Water Project Feather River water (~80–120 mg/L). The Irvine Basin alluvial groundwater — a system of interconnected Quaternary alluvial gravel and sand lenses beneath the Irvine Ranch — carries moderate dissolved mineral content from the local San Joaquin Hills geology (Tertiary marine sedimentary rock formations). The resulting IRWD blend delivers a moderately hard, moderate-TDS supply to the Irvine master-planned communities.

At 146 mg/L, Northwood's water is moderately hard — scale builds in kettles and appliances over months, dishwashers benefit from rinse aid, and bathroom fixtures develop calcium deposits. Quarterly descaling of heating appliances is the standard schedule. The PFAS level of 6.1 ppt warrants a certified drinking water filter — Orange County's military and aerospace industrial legacy (MCAS El Toro, now the Great Park), the former Tustin Marine Corps Air Station, and the Orange County industrial corridor contribute to the Irvine-area PFAS baseline in the IRWD supply.