Killingly Center Water Hardness & Quality Report (2026)

Killingly Center, Connecticut, in the Northeastern Connecticut Planning Region — a community in Killingly, a Windham County town adjacent to Putnam and Thompson in the Quiet Corner of northeast Connecticut — receives its municipal water from the Killingly Water Division, drawing from Killingly Pond or the Quinebaug River (Windham County) through the Killingly treatment system.

The moderately soft 99 mg/L hardness and TDS of 259.7 mg/L (high TDS for this hardness) reflect the northeast Connecticut mixed crystalline-sedimentary supply. The Killingly Pond watershed drains the Connecticut Eastern Uplands — Precambrian Avalon Terrane gneiss (insoluble crystalline — primary), and minor Cambrian Hopping Brook Formation. The elevated TDS relative to hardness suggests some organic loading or ionic contribution from the watershed, consistent with northeast Connecticut reservoir systems.

At 99 mg/L, Killingly Center's water is moderately soft — light scale forms slowly in appliances, dishwashers remain efficient, and bathroom fixtures need occasional cleaning. Semi-annual descaling is appropriate. The PFAS level of 11.9 ppt warrants a certified reverse osmosis drinking water filter — Naval Submarine Base New London (Groton CT — AFFF, the dominant southeast Connecticut PFAS source with plumes reaching into the Quinebaug-Thames watershed), the Killingly industrial complex on the Quinebaug River, and northeast Connecticut's PFAS-impacted water system produce Killingly Center's very elevated readings.