WH

Water Hardness in 94515

Calistoga, California · Napa County

86 PPM
5 GPG
Slightly Hard
0Soft60120180300+
Verified — State Lab Tested

Dataset updated March 9, 2026Matched to 4 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 4 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
1 verified treated-water source
4 matched systems total for this ZIP; treated-water reports are prioritized when available.
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
Report years 2024
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 94515

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.

4 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.
Napa, City Of
CA2810003
Slightly Hard
78 PPMsurface water84,804 servedVerified — State Lab Tested
Source water: 81 PPM
American Canyon, City Of
CA2810005
Slightly Hard
81 PPMsurface water21,437 servedHigh Confidence — USGS Monitoring
Calistoga, City Of
CA2810002
Hard
235 PPMsurface water5,610 servedHigh Confidence — USGS Monitoring
Tucker Acres Mutual Water Co.
CA2800516
Hard
235 PPMgroundwater200 servedHigh Confidence — USGS Monitoring

Nearby Zip Codes

95404126954612359457678945087994567789540912695403126945747895492126954391269540512695448126

What This Means For You

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

Slightly Hard Water

Your water is slightly hard. You may notice minor spotting on dishes or a slight film on faucets. A water softener is optional but can improve water quality.

Recommended Products

Water Hardness Test Kit
Our PickVarify (150 Strips)Also GreatJNW Direct (150 Strips)
Salt-Free Water Conditioner
Our PickSpringWell Salt-Free Cartridge

Learn more: Do I Need a Water Softener? | Salt-Based vs Salt-Free | How to Test Your 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 Calistoga, CA (94515).

Submit Your Data

Frequently Asked Questions

Is the water hard in Calistoga, CA (94515)?

The average water hardness in 94515 is 86 PPM (5 GPG), which is classified as slightly hard.

Do I need a water softener in 94515?

At 86 PPM, your water is relatively soft. A water softener is generally not necessary.

Is hard water in 94515 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 94515?

Zip code 94515 in Calistoga, California is served by 4 water systems.

Learn More About Your Water

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

Best Water Hardness Test Kits (2026 Reviews)

We compared test strips, liquid drop kits, TDS meters, and lab tests. Here's which testing method gives you the most accurate hardness reading.

8 min read

Hard Water vs Soft Water: Key Differences

Compare hard water and soft water by minerals, taste, soap lather, skin, hair, plumbing, and treatment needs.

10 min read