Londonderry Water Hardness & Quality Report (2026)

Londonderry, New Hampshire receives its water supply from Pennichuck Water Works, which sources treated water from Manchester Water Works. The primary source is Lake Massabesic, a surface reservoir located in Auburn and East Manchester. This important watershed, nestled in southeastern New Hampshire's glacially-carved landscape, provides the raw water that undergoes standard purification processes, including chlorination and fluoridation, at the treatment facility before distribution to Londonderry residents. Pennichuck Water Works also manages the distribution network and is actively involved in lead service line replacement.

The region's geology is characterized by Precambrian metamorphic bedrock, primarily composed of schist and gneiss formations. With minimal carbonate minerals present in these crystalline bedrock types, the water naturally remains soft. This geological makeup, common throughout New England's granitic terrain, means that minerals like calcium and magnesium, which contribute to water hardness, are not significantly picked up as the water flows through the watershed and surface systems into Lake Massabesic.

Because Londonderry's water is soft, homeowners typically experience fewer issues with limescale buildup on faucets, showerheads, and inside appliances like coffee makers and water heaters. Detergents and soaps lather easily, meaning you might use less product. While most households find soft water perfectly suitable, some residents may opt for point-of-use filters for specific needs. It's worth noting that trace levels of disinfection byproducts and PFOA/PFAS have been detected within legal limits. Residents concerned about these or other water quality aspects are encouraged to review the town's latest water quality reports and public meeting minutes.