Somerville Water Hardness & Quality Report (2026)

The Somerville Water Department, operating as part of the Massachusetts Water Resources Authority (MWRA) system, serves 81,045 residents across Somerville, Massachusetts. Water is purchased from the MWRA, drawn from the Quabbin Reservoir and Wachusett Reservoir systems in central Massachusetts, which form the backbone of the region's supply infrastructure. The system distributes water through 118 miles of water mains, 1,500 fire hydrants, and 15,600 service connections throughout the city.

The Quabbin and Wachusett watershed areas are underlain by Precambrian metamorphic bedrock — gneiss, schist, and granite — characteristic of the New England Upland physiographic province. This crystalline bedrock geology contributes minimal dissolved minerals, limiting the dissolution of calcium and magnesium-bearing minerals. The result is a naturally soft water supply with low mineral concentrations that requires no significant hardness treatment before distribution.

At soft hardness levels, Somerville residents experience minimal scale buildup in pipes, water heaters, and appliances, with reduced soap and detergent consumption for laundry and dishwashing. The MWRA explicitly recommends that customers do not need to install water softeners for clothes washing or dishwashing machines; new dishwashers can be configured for soft water to further reduce detergent use. Occasional red water events from main breaks or flow changes cause temporary rust-colored discoloration, typically clearing within hours. The utility employs chloramines, hypochlorite, ozone, and UV light for disinfection; lead and copper testing returned 6.62 ppb at the 90th percentile, well under the Action Level.