How hard is the water in Hillsborough, NJ?

Tap water hardness
100mg/L
5.8gpg
Moderately hard

Reported by NJ American Water - Raritan · October 2025

NJ typical
80 mg/L
EPA health violations since 2016
0
Softener for 3 people
24k grain
Data
Utility report

Tap water in Hillsborough has about 100 mg/L of hardness, which is 5.8 grains per gallon. On the USGS scale that counts as moderately hard. The number comes from NJ American Water - Raritan, dated October 2025.

Hillsborough on the hardness scale, with nearby cities
060120180240300360+NJ typical 80Belle Mead: 100 mg/LBelle Mead 100Manville: 100 mg/LManville 100Raritan: 100 mg/LRaritan 100Bradley Gardens: 100 mg/LBradley Gardens 100Neshanic Station: 100 mg/LNeshanic Station 100Somerville: 100 mg/LSomerville 100Finderne: 100 mg/LFinderne 100Bridgewater Center: 100 mg/LBridgewater Center 100Blackwells Mills: 111 mg/LBlackwells Mills 111Franklin Center: 111 mg/LFranklin Center 111Hillsborough 100mg/L as calcium carbonate060120180240300360+NJ 80Belle Mead: 100 mg/LBelle Mead 100Manville: 100 mg/LManville 100Raritan: 100 mg/LRaritan 100Bradley Gardens: 100 mg/LBradley Ga. 100Neshanic Station: 100 mg/LNeshanic S. 100Blackwells Mills: 111 mg/LBlackwells. 111100 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 100 mg/L, Hillsborough is 20 mg/L above the typical New Jersey figure of 80. None of the 10 nearest cities we track has softer water. The range nearby runs from 100 mg/L in Belle Mead to 111 in Blackwells Mills.

What 100 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 Hillsborough

3 people × 75 gallons a day × 5.8 gpg = 1,316 grains a day. A 24,000-grain unit regenerates about every 18 days.

Size it for your household

EPA record for Hillsborough's water system

NJ American Water - Raritan · PWSID NJ2004002

No health-based violations since 2016

Serves about 615,430 people from surface water.

Health-based
0
Monitoring or reporting
2
Open now
0

TapWaterData ties Hillsborough to this system. EPA's service-area records do not name Hillsborough, so check the utility printed on your water bill.

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 Hillsborough water hard?

Somewhat. It measures about 100 mg/L (5.8 grains per gallon), which the USGS classes as moderately hard.

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

About 5.8 gpg. One grain per gallon equals 17.1 mg/L, so 100 mg/L divided by 17.1 gives 5.8.

What size water softener do I need in Hillsborough?

For 3 people using 75 gallons each per day, 5.8 gpg works out to about 1,316 grains a day. A 24,000-grain softener covers that with a regeneration about every 18 days.

Has the Hillsborough water system had EPA violations?

EPA records show no health-based violations for NJ American Water - Raritan since 2016. There were also 2 monitoring or reporting violations, which are about late or missing tests and notices.

Nearby cities

All 227 cities in New Jersey

Hardness data: TapWaterData US Water Hardness (utility report, October 6, 2025), CC BY 4.0. Population: US Census Bureau. Violations: EPA ECHO. How we use them.