Dedham Water Hardness & Quality Report (2026)

Dedham, Massachusetts, in Norfolk County southwest of Boston on the Neponset River, receives its municipal water from Dedham-Westwood Water District, which draws from MWRA wholesale supply (Quabbin and Wachusett reservoirs) blended with local surface water from Neponset River watershed reservoirs including Wigwam Pond and other local impoundments in the Dedham area. The Neponset River flows along Dedham's southern boundary, draining the Blue Hills Reservation and surrounding Norfolk County highlands before entering Boston Harbor. Both the MWRA supply and local Neponset watershed contribute to the community's drinking water.

The moderately soft 90.5 mg/L hardness reflects the composite character of Dedham's blended supply. Quabbin Reservoir supply is very soft (~50–60 mg/L) from its central Massachusetts Precambrian and Paleozoic crystalline rock watershed — granites, gneisses, and metavolcanics with essentially no carbonate content. Local Neponset watershed reservoirs add some mineral enrichment from the Blue Hills granite and hornfels terrain, and alkalinity management during treatment adds modest hardness. The blended result falls in the comfortable moderately soft range across the Dedham-Westwood service area.

At 90.5 mg/L, Dedham's water is moderately soft — a practical and comfortable supply for everyday household use. Soap lathers well, appliances accumulate scale slowly, and glassware from the dishwasher shows only occasional light spotting. Semi-annual descaling of kettles and coffee machines is adequate under normal use. The significant concern for Dedham residents is the elevated PFAS level of 9.4 ppt — the I-95 and Route 128 technology and industrial corridor running through Norfolk County has produced measurable PFAS detections throughout the region. Residents should use a certified reverse osmosis or high-performance activated carbon filter for daily drinking and cooking water.