Wilmington Water Hardness & Quality Report (2026)

Wilmington, Massachusetts, in Middlesex County north of Woburn and Burlington — a suburban Middlesex County town in the northern Route 128/I-93 technology corridor, historically a chemical and industrial manufacturing center — receives its municipal water from the Wilmington Water Department, which draws from local Ipswich River watershed reservoirs or from the Massachusetts Water Resources Authority (MWRA) metropolitan supply system. Wilmington's supply may blend local reservoir water and MWRA Cosmo Reservoir/Wachusett Reservoir supply.

The moderately hard 112.5 mg/L hardness and TDS of 288.3 mg/L are higher than expected for New England crystalline bedrock watersheds, reflecting the moderately mineralized character of the Ipswich-Mystic watershed with some supply blending effects. The Ipswich River watershed and the Upper Mystic Lake area drain the Proterozoic Avalonian terrane of northeastern Massachusetts — ancient Avalonian volcanic and metasedimentary rocks (the Salem Gabbro-Diorite and Dedham Granite of the eastern Massachusetts Avalonian basement) with minimal carbonate minerals. However, MWRA supply from the Wachusett Reservoir (central Massachusetts) adds slightly more mineralized water, and the Middlesex County glacial till covering the watershed contributes calcareous reworked material that sustains the moderate hardness.

At 112.5 mg/L, Wilmington's water is moderately hard for New England — consistent with the Route 128 suburban Middlesex County supply. Scale builds in kettles and appliances over months, the dishwasher benefits from rinse aid, and faucet aerators need occasional cleaning. Quarterly descaling of heating appliances is appropriate. The critically elevated PFAS level of 10.9 ppt requires urgent attention — Wilmington is home to the former Olin Corporation (Winchester Arms) ammunition manufacturing plant, which is a documented major PFAS source in the Middlesex County area, contributing to some of Massachusetts's most elevated municipal PFAS readings. A certified reverse osmosis drinking water filter is strongly recommended.