Greenwich Water Hardness & Quality Report (2026)

Greenwich, Connecticut, in Western Connecticut — a Western Connecticut Planning Region town adjacent to Stamford and New Canaan in southwest Connecticut — receives its water from the Aquarion Water Company, drawing from Byram Lake or Mianus Reservoir (Western Connecticut) through the southwest Connecticut distribution.

The very soft 33.5 mg/L hardness and very low TDS of 58.6 mg/L reflect the southwest Connecticut Byram-Mianus watershed supply's very soft character — similar to Shadow Hills CA (33.5/58.6), the Precambrian Monson Gneiss with minimal Cambrian Stockbridge Marble calcareous contact produces very soft water typical of the Connecticut shoreline communities drawing from the Precambrian Highlands. The Byram-Mianus watershed at Western Connecticut — Precambrian Monson Gneiss (insoluble — primary dilutant), Cambrian Stockbridge Marble (slightly calcareous — minor hardness contributor), and Pleistocene Connecticut glacial drift (insoluble — secondary dilutant).

At 33.5 mg/L, Greenwich's water is very soft — scale forms very slowly in appliances, dishwashers remain efficient, and no softening is needed. Annual descaling is appropriate. The PFAS level of 6.2 ppt warrants a certified drinking water filter — the Greenwich southwest Connecticut corporate and industrial corridor contribute to Greenwich's elevated PFAS readings.