Portsmouth Water Hardness & Quality Report (2026)

Portsmouth, New Hampshire, in Rockingham County — New Hampshire's only seaport city, one of the oldest cities in the United States (settled 1623), home to the Portsmouth Naval Shipyard, the historic Strawbery Banke Museum district, and the Piscataqua River seacoast gateway — receives its municipal water from the Portsmouth Water Division, which draws from the Bellamy Reservoir on the Bellamy River and local southeastern New Hampshire watershed impoundments in Rockingham County. Portsmouth's water supply reflects the New Hampshire Seacoast Region's exceptional crystalline rock terrain.

The very soft 42 mg/L hardness and low TDS of 83.9 mg/L are consistent with the New Hampshire Seacoast Region's Avalonian granite watershed character — softer than most northeastern US cities and comparable to the exceptional Derry NH supply (18 mg/L). The Bellamy Reservoir watershed drains the Proterozoic Avalonian terrane of southeastern New Hampshire — the Rye Complex (Proterozoic Avalonian gneiss and quartzite of the Seacoast Region), the Newburyport Batholith (Carboniferous granite), and related low-carbonate crystalline formations. New Hampshire's coastal zone receives abundant precipitation (44+ inches/year) over forested, protected watershed lands, maintaining exceptionally soft, clean source water. The slightly higher hardness (42 mg/L) compared to Derry (18 mg/L) reflects the Bellamy watershed's different crystalline unit compositions and the distribution system's modest mineral contribution.

At 42 mg/L, Portsmouth's water is very soft — excellent for all household applications. Scale forms very slowly, soap lathers abundantly, and the dishwasher operates at peak efficiency. Annual descaling of heating appliances is sufficient. The PFAS level of 5.8 ppt warrants a certified drinking water filter — Portsmouth Naval Shipyard (a major Navy facility with decades of AFFF firefighting foam use), Pease Air Force Base (formerly Pease AFB, now Pease International Tradeport — one of the first US sites where PFAS contamination in drinking water was publicly confirmed), and the Rockingham County military-industrial legacy make Portsmouth's PFAS level a matter of active public health concern in New Hampshire.