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Water Hardness in 06378

Stonington, Connecticut · New London County

29 PPM
1.7 GPG
Soft
0Soft60120180300+
High Confidence — USGS Monitoring

Dataset updated March 9, 2026Matched to 6 water systemsTap readings can vary by utility zone, treatment, and plumbing. Methodology

Source context

How this ZIP reading is built

This ZIP reading is built from 6 matched water systems. When more than one system is matched, the displayed value is weighted toward larger known service populations when that data is available.

Source basis
4 USGS-backed sources
6 matched systems total for this ZIP; USGS monitoring is used where treated-water reports are unavailable.
Water source profile
Primarily surface water
Surface-water hardness can shift with reservoirs, runoff, season, and treatment. This profile is weighted by known population served across matched systems.
Data recency
March 9, 2026
Dataset rebuilt March 9, 2026; individual utility reporting years can vary.

Hardness is a mineral-content reading, not a drinking-water safety rating. Use it for scale, appliance, and softener decisions; check your utility report or test your tap before sizing treatment equipment. See how we calculate local readings.

Water Systems Serving 06378

These are the systems matched to this ZIP code. The displayed ZIP value is weighted toward larger known service populations when population data is available.

6 water systems
PWSID is the public water system identifier. Data Source shows whether the hardness value comes from a treated-water report, USGS monitoring, or a local estimate; source year is shown when available.
Norwich Public Utilities
CT1040011
Soft
26 PPMsurface water36,163 servedHigh Confidence — USGS Monitoring
Groton Utilities
CT0590011
Soft
26 PPMsurface water30,200 servedEstimated — Nearby Data
New London Dept. Of Public Utilities
CT0950011
Soft
29 PPMsurface water27,620 servedEstimated — County Avg
Waterford Wpca
CT1520071
Soft
24 PPMsurface water16,578 servedHigh Confidence — USGS Monitoring
East Lyme Water & Sewer Commission
CT0450011
Soft
24 PPMsurface water15,245 servedHigh Confidence — USGS Monitoring
Showing the first 5 systems. Expand to review all matched systems.

Nearby Zip Codes

063792906355290633929063592902891460634029028044606335290280846028334606320290636529

What This Means For You

Recommendations are based on the displayed ZIP hardness reading. Confirm your tap reading before sizing or buying treatment equipment.

Your Water Is Soft

Your water hardness is in the soft range. You likely don't need a water softener. Enjoy your naturally soft water!

Know your water hardness?

If you've tested your water or have your utility's CCR report, share your reading to help us improve accuracy for Stonington, CT (06378).

Submit Your Data

Frequently Asked Questions

Is the water hard in Stonington, CT (06378)?

The average water hardness in 06378 is 29 PPM (1.7 GPG), which is classified as soft.

Do I need a water softener in 06378?

At 29 PPM, your water is relatively soft. A water softener is generally not necessary.

Is hard water in 06378 safe to drink?

Water hardness itself is a mineral-content reading, not a drinking-water safety rating. Calcium and magnesium are naturally occurring minerals, but you should check your utility's Consumer Confidence Report for contaminant and compliance information.

How many water systems serve 06378?

Zip code 06378 in Stonington, Connecticut is served by 6 water systems.

Learn More About Your Water

Water Hardness Scale: PPM and GPG Chart

Use the USGS water hardness scale to compare PPM, GPG, and mg/L levels from soft to very hard water.

10 min read

How to Test Water Hardness at Home

Compare free lookups, soap tests, test strips, liquid drop kits, and lab tests for measuring water hardness.

8 min read