Derry Village Water Hardness & Quality Report (2026)

The Town of Derry Water Department (PWS ID 0611010) serves approximately 34,000 residents in Derry, New Hampshire, Rockingham County. The Core Water System sources supply from Beaver Lake surface water and multiple groundwater wells. Treatment occurs at facilities managed by the department, with annual testing detailed in Consumer Confidence Reports available on the official town website.

Beaver Lake lies within the Lamprey River watershed, part of the broader Piscataqua River basin draining to the Atlantic. Groundwater originates from glacial aquifers and fractured bedrock in the Merrimack Valley region. Devonian granite and schist formations dominate — including the Kinsman Quartz Monzonite and New Hampshire Plutonic Series — with glacial sands providing recharge zones. This geology imparts a moderately mineralized profile to the mixed supply, as calcium and magnesium dissolve from silicate minerals and glacial sediments, contrasting with softer rainwater-dominated sources elsewhere in the state.

Moderately hard water leads to moderate scale buildup in appliances like water heaters, dishwashers, and washing machines, reducing efficiency over time. Faucet aerators and showerheads may clog, while laundry and dishwashing require more detergent. Regular descaling with vinegar, installing drain screens, and flushing water heaters biannually help mitigate issues. A water softener is often recommended for households noticing spots on glassware, film on fixtures, or dry skin. Derry's tap water complies with all EPA Maximum Contaminant Levels per 2021 testing; however, several contaminants exceed EWG health guidelines including hexavalent chromium and low-level PFAS. Treatment involves disinfection, coagulation, and corrosion control; pH is typically neutral and lead/copper rule compliance has been achieved.