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Water Hardness in New Hampshire

Across 7 measured cities — with 83 more covered by labeled county-level estimates — New Hampshire's median tap water hardness is 31.4 mg/L (1.8 gpg): soft on the USGS scale. Below: every covered city, the state's hardest and softest water, and the geology that explains it.

Data updated July 6, 2026. Sources: utility-reported water quality data and USGS/EPA Water Quality Portal samples.

State Median
31.4
mg/L (1.8 gpg), measured cities
Measured Range
16.2-64.1
mg/L across measured cities
Measured Cities
7
utility-reported or computed values
County Estimates
83
92% of covered cities

New Hampshire Cities by Hardness Category

Measured cities only — labeled county estimates never enter the category counts or the median.

CategoryRangeMeasured citiesShare
Soft0-60 mg/L685.7%
Moderately hard60-120 mg/L114.3%
Hard120-180 mg/L00.0%
Very hard>180 mg/L00.0%

Hardest and Softest Water in New Hampshire

Measured values only; labeled county estimates and values under active dispute never rank.

Hardest water in New Hampshire

  1. Dover — 64.1 mg/L (3.8 gpg), moderately hard
  2. Merrimack — 33.0 mg/L (1.9 gpg), soft
  3. East Merrimack — 31.4 mg/L (1.8 gpg), soft
  4. Nashua — 31.4 mg/L (1.8 gpg), soft
  5. Hudson — 31.0 mg/L (1.8 gpg), soft

Softest water in New Hampshire

  1. Manchester — 16.2 mg/L (0.9 gpg), soft
  2. Lebanon — 22.2 mg/L (1.3 gpg), soft
  3. Hudson — 31.0 mg/L (1.8 gpg), soft
  4. East Merrimack — 31.4 mg/L (1.8 gpg), soft
  5. Nashua — 31.4 mg/L (1.8 gpg), soft

Every Covered City in New Hampshire

All 90 covered New Hampshire cities, sorted by population served. "County estimate" rows are labeled context values from USGS/EPA Water Quality Portal county sampling — they never enter the median above. City names link to each city's full water quality page.

CityHardness (mg/L)gpgCategoryData
Manchester16.20.9SoftUtility-reported
Nashua31.41.8SoftUtility-reported
East Merrimack31.41.8SoftUtility-reported
Hudson31.01.8SoftUtility-reported
Dover64.13.8Moderately hardUtility-reported
Rollinsford19.71.1SoftCounty estimate
Rochester19.71.1SoftCounty estimate
Merrimack33.01.9SoftUtility-reported
Laconia34.02.0SoftCounty estimate
Durham19.71.1SoftCounty estimate
Exeter123.07.2HardCounty estimate
Seabrook123.07.2HardCounty estimate
Somersworth19.71.1SoftCounty estimate
Lebanon22.21.3SoftUtility-reported
Berlin14.80.9SoftCounty estimate
Milford18.01.1SoftCounty estimate
Plymouth14.60.8SoftCounty estimate
Newmarket123.07.2HardCounty estimate
Newport22.81.3SoftCounty estimate
Raymond123.07.2HardCounty estimate
Goffstown18.01.1SoftCounty estimate
Meredith34.02.0SoftCounty estimate
Hooksett13.30.8SoftCounty estimate
Jaffrey14.90.9SoftCounty estimate
Bristol14.60.8SoftCounty estimate
Grantham22.81.3SoftCounty estimate
Farmington19.71.1SoftCounty estimate
Waterville Valley14.60.8SoftCounty estimate
Winchester14.90.9SoftCounty estimate
Lincoln14.60.8SoftCounty estimate
New London13.30.8SoftCounty estimate
North Woodstock14.60.8SoftCounty estimate
Gorham14.80.9SoftCounty estimate
Groveton14.80.9SoftCounty estimate
Henniker13.30.8SoftCounty estimate
Charlestown22.81.3SoftCounty estimate
Tilton13.30.8SoftCounty estimate
Lancaster14.80.9SoftCounty estimate
Enfield14.60.8SoftCounty estimate
Hillsborough18.01.1SoftCounty estimate
Hinsdale14.90.9SoftCounty estimate
Ashland14.60.8SoftCounty estimate
Bethlehem14.60.8SoftCounty estimate
Wilton18.01.1SoftCounty estimate
Whitefield14.80.9SoftCounty estimate
Epping123.07.2HardCounty estimate
Campton14.60.8SoftCounty estimate
Holderness14.60.8SoftCounty estimate
Sanbornville7.20.4SoftCounty estimate
Colebrook14.80.9SoftCounty estimate
Madison7.20.4SoftCounty estimate
Troy14.90.9SoftCounty estimate
Greenville18.01.1SoftCounty estimate
Walpole14.90.9SoftCounty estimate
Lisbon14.60.8SoftCounty estimate
Warner13.30.8SoftCounty estimate
Meriden22.81.3SoftCounty estimate
North Walpole14.90.9SoftCounty estimate
New Hampton34.02.0SoftCounty estimate
Moultonborough7.20.4SoftCounty estimate
Jackson7.20.4SoftCounty estimate
Derry123.07.2HardCounty estimate
Amherst18.01.1SoftCounty estimate
Hampton123.07.2HardCounty estimate
Alton34.02.0SoftCounty estimate
Weare18.01.1SoftCounty estimate
Bedford18.01.1SoftCounty estimate
Lyme14.60.8SoftCounty estimate
Center Harbor34.02.0SoftCounty estimate
Plainfield22.81.3SoftCounty estimate
Northwood123.07.2HardCounty estimate
West Ossipee7.20.4SoftCounty estimate
Windham123.07.2HardCounty estimate
Portsmouth123.07.2HardCounty estimate
Warren14.60.8SoftCounty estimate
Stratham123.07.2HardCounty estimate
Conway7.20.4SoftCounty estimate
Glen7.20.4SoftCounty estimate
Atkinson123.07.2HardCounty estimate
Keene14.90.9SoftCounty estimate
Salem123.07.2HardCounty estimate
Barrington19.71.1SoftCounty estimate
Sandown123.07.2HardCounty estimate
Tamworth7.20.4SoftCounty estimate
Sunapee22.81.3SoftCounty estimate
Concord13.30.8SoftCounty estimate
Thornton14.60.8SoftCounty estimate
Intervale7.20.4SoftCounty estimate
Gilford34.02.0SoftCounty estimate
Woodsville14.60.8SoftCounty estimate

Above 120 mg/L (7 gpg), scale is usually worth treating — see our water softener guide, or size a system with the hardness calculator & converter.

The Geology Behind New Hampshire's Water Hardness

New Hampshire sits in the New England crystalline uplands region.

New England sits on granite, gneiss, and schist - crystalline bedrock with almost no carbonate minerals for water to dissolve. Ample rain and snowmelt move quickly through thin, glacially scoured soils into rivers and upland reservoirs without picking up much calcium or magnesium. That is why the USGS maps this region among the softest water in the country.

Source: USGS Water Science School - Hardness of Water

New Hampshire Water Hardness FAQ

Does New Hampshire have hard water?

On the whole, no — New Hampshire's statewide median sits below the hard threshold, though some cities run harder. The median is 31.4 mg/L (1.8 gpg) — soft on the USGS scale, where anything above 120 mg/L (7 gpg) counts as hard. 0 of New Hampshire's 7 measured cities fall in the hard or very hard bands (0%), so check your own city rather than the state average.

How hard is tap water in New Hampshire?

Across the 7 New Hampshire cities with measured values in our index, the median hardness is 31.4 mg/L (1.8 gpg) — soft on the USGS scale. Individual cities range from 16.2 to 64.1 mg/L, so check your own city rather than assuming the state number.

Which city in New Hampshire has the hardest water?

Dover has the hardest measured tap water in our New Hampshire index at 64.1 mg/L (3.8 gpg) — moderately hard on the USGS scale. Rankings use measured utility values only; labeled county estimates and values under active dispute are excluded.

Do I need a water softener in New Hampshire?

0 of New Hampshire's 7 measured cities (0%) fall in the hard or very hard bands — above 120 mg/L (7 gpg), the level where most water treatment professionals suggest considering an ion-exchange softener. Hardness varies utility to utility, so look up your own city's value before sizing equipment.

How do I find my city's exact water hardness?

Enter your ZIP code in our free lookup at tapwaterdata.com/zip to see the value we hold for your New Hampshire city from utility-reported water quality data, check your water utility's annual Consumer Confidence Report (CCR), or use a home test-strip kit.

← Water hardness across the USInteractive hardness mapCalculator & converterFree ZIP-code hardness lookupData & methodology

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