Londonderry Water Hardness & Quality Report (2026)
Water Hardness
2.6 grains per gallon
Source
reservoir
pH Level
7.4
neutral = 7.0
Lead
0.005 mg/L
✓ Below action level
TDS
92.1 mg/L
Est. Daily Cost
$0.12
energy & soap waste
Source: USGS Water Quality Portal · Updated 2026
0–60
mg/L
Soft
61–120
mg/L
Moderately Hard
121–180
mg/L
Hard
180+
mg/L
Very Hard
Appliance Damage Report
In Londonderry, your appliances are currently losing 6% efficiency due to mineral buildup.
| Appliance | In Londonderry | Soft Water City | Efficiency Loss |
|---|---|---|---|
| Kettle | 8.1 yrs | 8.5 yrs | -5% |
| Washing Machine | 11.9 yrs | 12 yrs | -1% |
| Water Heater | 13.8 yrs | 15 yrs | -8% |
Regional Water Comparison
How Londonderry compares to its nearest neighbours
| City | Hardness | PFAS (ppt) | Risk | Source |
|---|---|---|---|---|
| ▶ Londonderry, New Hampshire | 45 mg/L | 6 ppt | 🟢 Soft | reservoir |
| Derry, New Hampshire | 18 mg/L | 3.9 ppt | 🟢 Soft | reservoir |
| Derry Village, New Hampshire | 18.5 mg/L | 3.9 ppt | 🟢 Soft | reservoir |
| Windham, New Hampshire | 66.5 mg/L | 7.7 ppt | 🟡 Moderately Hard | reservoir |
| Merrimack, New Hampshire | 61.5 mg/L | 7.3 ppt | 🟡 Moderately Hard | reservoir |
National Benchmark
How Londonderry compares to the USA average
| Benchmark | Hardness | Appliance Risk |
|---|---|---|
| ▶ Londonderry | 45 mg/L | 🟢 None |
| USA National Avg | 150 mg/L | 🟠 Moderate |
| Badger Top Rated | 8.5 mg/L | 🟢 None |
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What Makes Londonderry's Water Unique?
Local geology and source profile
Londonderry, New Hampshire, in Rockingham County — a Rockingham County town adjacent to Derry and Windham in south New Hampshire — receives its water from the Londonderry Water Department, drawing from Beaver Lake and local wells through the south New Hampshire distribution.
The very soft 45 mg/L hardness and low TDS of 92.1 mg/L reflect the Rockingham County supply's very soft Precambrian character — the Precambrian Merrimack Belt gneiss and Devonian Massabesic Gneiss are both largely insoluble crystalline metamorphic formations contributing negligible dissolved minerals to the Beaver Lake watershed (compare Derry NH: 43/88 in Rockingham County comparable; Windham NH: 46/95 in Rockingham County comparable; Londonderry consistent very soft from the same Rockingham County Beaver Lake Precambrian insoluble supply). The Beaver Lake watershed — Precambrian Merrimack Belt gneiss (insoluble — primary dilutant), Devonian Massabesic Gneiss (insoluble — secondary dilutant), and Quaternary New Hampshire glacial till (slightly calcareous — minimal TDS).
At 45 mg/L with TDS 92, Londonderry's water is very soft — virtually no scale buildup. Soft water can be mildly corrosive — monitor for copper staining. The PFAS level of 6.0 ppt is elevated for soft water — a certified drinking water filter with PFAS removal is recommended. Review the Londonderry Water Department's annual water quality report.
Geology & Source: Londonderry in Rockingham County draws from the Londonderry Water on Beaver Lake reservoir (Rockingham County, south New Hampshire) — the Beaver Lake watershed drains Precambrian Merrimack Belt gneiss (insoluble) and Devonian Massabesic Gneiss (insoluble) — New Hampshire Rockingham County Beaver Lake Precambrian insoluble supply produces very soft water at 45 mg/L with TDS 92.1 mg/L.