Lexington Water Hardness & Quality Report (2026)

Lexington, Massachusetts is served by the Massachusetts Water Resources Authority (MWRA), a regional public water utility headquartered at 201 Bedford Street, Lexington, MA 02420. The primary water source is Quabbin Reservoir, a major surface-water impoundment in central Massachusetts. MWRA supplies 32,271 people across Lexington and surrounding communities in Middlesex County. Water treatment includes chloramines, hypochlorite, ozone, and UV light disinfection to ensure safety and compliance with EPA standards.

The Quabbin Reservoir watershed is situated on Precambrian metamorphic and granitic bedrock typical of the New England uplands, overlain by glacial deposits from the last ice age. This crystalline geology contains few soluble minerals such as limestone or dolomite, resulting in naturally soft water chemistry. The watershed's granitic composition and lack of carbonate-rich formations mean the water picks up minimal dissolved calcium and magnesium as it flows through soil and rock, producing a supply with characteristically low mineral content.

Lexington's water is soft, meaning scale buildup in pipes and appliances is minimal and soap lathers readily without excessive use. Residents typically do not require water softening treatment, and the supply is gentler on plumbing and heating systems, reducing maintenance costs and extending appliance lifespan. As of October 2023, MWRA testing detected only trace amounts of some PFAS and no detectable amounts of others, well below the EPA's 4 parts per trillion maximum contaminant level. All contaminants tested are within EPA Maximum Contaminant Level Goals and safe according to health-based guidelines. MWRA employs a source-protection strategy to prevent pollutant entry rather than relying solely on removal after contamination.