How hard is the water in Manhasset, NY?

Tap water hardness
66mg/L
3.9gpg
Moderately hard

Reported by WA of Western Nassau · October 2025

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

The water in Manhasset carries roughly 66 mg/L of dissolved calcium and magnesium, or 3.9 grains per gallon. That is moderately hard water. The number comes from WA of Western Nassau, dated October 2025.

Manhasset on the hardness scale, with nearby cities
060120180240300360+NY typical 31Garden City Park: 51 mg/LGarden City Park 51Great Neck Plaza: 55 mg/LGreat Neck Plaza 55Great Neck: 55 mg/LGreat Neck 55North New Hyde Park: 55 mg/LNorth New Hyde Park 55Roslyn Heights: 55 mg/LRoslyn Heights 55Williston Park: 55 mg/LWilliston Park 55Kings Point: 55 mg/LKings Point 55East Hills: 56 mg/LEast Hills 56Port Washington: 59 mg/LPort Washington 59North Hills: 66 mg/LNorth Hills 66Manhasset 66mg/L as calcium carbonate060120180240300360+NY 31Great Neck Plaza: 55 mg/LGreat Neck. 55Great Neck: 55 mg/LGreat Neck 55North New Hyde Park: 55 mg/LNorth New. 55Roslyn Heights: 55 mg/LRoslyn Hei. 55Port Washington: 59 mg/LPort Washi. 59North Hills: 66 mg/LNorth Hills 6666 mg/Lmg/L as calcium carbonate
Soft 0–60 mg/LModerately hard 61–120 mg/LHard 121–180 mg/LVery hard 181+ mg/L

Manhasset sits 35 mg/L above the typical New York figure of 31. None of the 10 nearest cities we track has harder water. The range nearby runs from 51 mg/L in Garden City Park to 66 in North Hills.

What 66 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 Manhasset

3 people × 75 gallons a day × 3.9 gpg = 875 grains a day. A 24,000-grain unit regenerates about every 27 days.

Size it for your household

EPA record for Manhasset's water system

WA of Western Nassau · PWSID NY2902830

No health-based violations since 2016

Serves about 120,000 people from groundwater.

Health-based
0
Monitoring or reporting
1
Open now
0

TapWaterData ties Manhasset to this system. EPA's service-area records do not name Manhasset, 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 Manhasset water hard?

Somewhat. It measures about 66 mg/L (3.9 grains per gallon), which the USGS classes as moderately hard.

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

About 3.9 gpg. One grain per gallon equals 17.1 mg/L, so 66 mg/L divided by 17.1 gives 3.9.

What size water softener do I need in Manhasset?

For 3 people using 75 gallons each per day, 3.9 gpg works out to about 875 grains a day. A 24,000-grain softener covers that with a regeneration about every 27 days.

Has the Manhasset water system had EPA violations?

EPA records show no health-based violations for WA of Western Nassau since 2016. There were also 1 monitoring or reporting violation, which are about late or missing tests and notices.

Nearby cities

All 149 cities in New York

Hardness data: TapWaterData US Water Hardness (utility report, October 15, 2025), CC BY 4.0. Population: US Census Bureau. Violations: EPA ECHO. How we use them.