How hard is the water in Marlborough, MA?

Tap water hardness
67mg/L
3.9gpg
Moderately hardCounty estimate

County estimate from 2,026 water samples in Middlesex County · July 2026

MA typical
38 mg/L
EPA health violations since 2016
0
Softener for 3 people
24k grain
Data
County estimate

Water samples from around Marlborough put hardness at about 67 mg/L (3.9 gpg), which would be moderately hard on the USGS scale. Treat this as a rough guide: it is the median of 2,026 samples taken across Middlesex County, mostly wells and streams, not a test of Marlborough's treated tap water. One more reason for caution: EPA lists Marlborough's water system as using surface water, which is often softer than the wells behind the county figure.

Marlborough on the hardness scale, with nearby cities
060120180240300360+MA typical 38Clinton: 14 mg/LClinton 14Waltham: 17 mg/LWaltham 17Milford: 37 mg/LMilford 37Worcester: 42 mg/LWorcester 42Framingham: 52 mg/LFramingham 52West Concord: 57 mg/LWest Concord 57Maynard: 86 mg/LMaynard 86Wellesley: 89 mg/LWellesley 89Cochituate: 93 mg/LCochituate 93Northborough: 110 mg/LNorthborough 110Marlborough 67mg/L as calcium carbonate060120180240300360+MA 38Clinton: 14 mg/LClinton 14Framingham: 52 mg/LFramingham 52West Concord: 57 mg/LWest Conco. 57Maynard: 86 mg/LMaynard 86Cochituate: 93 mg/LCochituate 93Northborough: 110 mg/LNorthborou. 11067 mg/Lmg/L as calcium carbonate
Soft 0–60 mg/LModerately hard 61–120 mg/LHard 121–180 mg/LVery hard 181+ mg/L

At 67 mg/L, Marlborough is 29 mg/L above the typical Massachusetts figure of 38. Of the 10 nearest cities we track, 6 have softer water and 4 have harder. The range nearby runs from 14 mg/L in Clinton to 110 in Northborough.

What 67 mg/L means at home

You may see faint white spots on glasses and shower doors after the water dries.

Scale builds up slowly. A kettle or coffee maker needs descaling now and then, maybe every few months.

Hardness is not a health problem, and EPA sets no limit for it. It is a matter of scale and soap.

What to do about it

Optional. Plenty of households at this level live with it and descale the kettle now and then.

Water softener

Worth a look if spots on glass bother you, or if your tankless water heater manual asks for softer water.

Carbon filter

Improves taste and removes chlorine. It leaves calcium and magnesium in place.

Softener size for Marlborough

3 people × 75 gallons a day × 3.9 gpg = 880 grains a day. A 24,000-grain unit regenerates about every 27 days.

Size it for your household

EPA record for Marlborough's water system

Marlborough DPW Water Div. (MWRA) · PWSID MA2170000

No health-based violations since 2016

Serves about 41,799 people from surface water.

Health-based
0
Monitoring or reporting
2
Open now
0

EPA lists this system as serving Marlborough.

Health-based means a contaminant above its legal limit or a missed treatment step. Monitoring and reporting violations are late or missing tests and notices. Source: EPA ECHO, 2026Q3 export, violations with periods starting 2016 or later. Full EPA record.

Questions

Is Marlborough water hard?

Somewhat. It measures about 67 mg/L (3.9 grains per gallon), which the USGS classes as moderately hard.

What is the water hardness in Marlborough in grains per gallon?

About 3.9 gpg. One grain per gallon equals 17.1 mg/L, so 67 mg/L divided by 17.1 gives 3.9.

What size water softener do I need in Marlborough?

For 3 people using 75 gallons each per day, 3.9 gpg works out to about 880 grains a day. A 24,000-grain softener covers that with a regeneration about every 27 days.

Has the Marlborough water system had EPA violations?

EPA records show no health-based violations for Marlborough DPW Water Div. (MWRA) since 2016. There were also 2 monitoring or reporting violations, which are about late or missing tests and notices.

Nearby cities

All 104 cities in Massachusetts

Hardness data: TapWaterData US Water Hardness (county estimate, July 4, 2026), CC BY 4.0. Population: US Census Bureau. Violations: EPA ECHO. How we use them.