Where does the water in 94010 come from?

Water for zip code 94010 in Hillsborough, California is provided by 25 water systems. Contact your local utility for specific source information, or check our detailed page for your area.

Water Hardness in 94010

Hillsborough, California · San Mateo County

119 PPM

7 GPG

Slightly Hard

0Soft60120180300+

Verified — State Lab Tested

Dataset updated March 9, 2026Matched to 25 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 25 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

6 verified treated-water sources

25 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 94010

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.

25 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.

Water System	Source	Hardness	Pop. Served	Data Source
Sfpuc City Distribution Division CA3810011	surface water	9 PPM Soft USGS estimate: 208 PPM	848,019	Verified — State Lab Tested(2024)
City Of Daly City CA4110013	surface water	216 PPM Hard	104,901	High Confidence — USGS Monitoring
California Water Service - San Mateo CA4110008	surface water	192 PPM Hard	102,348	High Confidence — USGS Monitoring
City Of Redwood City CA4110022	surface water	315 PPM Very Hard	92,819	High Confidence — USGS Monitoring
California Water Service-S San Francisco CA4110009	surface water	386 PPM Very Hard USGS estimate: 192 PPM	64,146	Verified — State Lab Tested(2024)

Sfpuc City Distribution Division

CA3810011

Soft

9 PPMsurface water848,019 servedVerified — State Lab Tested

Source water: 208 PPM

City Of Daly City

CA4110013

Hard

216 PPMsurface water104,901 servedHigh Confidence — USGS Monitoring

California Water Service - San Mateo

CA4110008

Hard

192 PPMsurface water102,348 servedHigh Confidence — USGS Monitoring

City Of Redwood City

CA4110022

Very Hard

315 PPMsurface water92,819 servedHigh Confidence — USGS Monitoring

California Water Service-S San Francisco

CA4110009

Very Hard

386 PPMsurface water64,146 servedVerified — State Lab Tested

Source water: 192 PPM

Showing the first 5 systems. Expand to review all matched systems.

Nearby Zip Codes

94030241 94401241 94402241 94128241 94403241 94066241 94002241 94038241 94404241 94044241 94080241 94037241

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 Hillsborough, CA (94010).

Submit Your Data

Frequently Asked Questions

Is the water hard in Hillsborough, CA (94010)?

The average water hardness in 94010 is 119 PPM (7 GPG), which is classified as slightly hard.

Do I need a water softener in 94010?

At 119 PPM, your water is relatively soft. A water softener is generally not necessary.

Is hard water in 94010 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 94010?

Zip code 94010 in Hillsborough, California is served by 25 water systems.