Belmont, CA water hardness

Tap water hardness
37mg/L
2.2gpg
Soft

Reported by California Water Service - San Mateo · October 2025

CA typical
121 mg/L
EPA health violations since 2016
0
Data
Utility report

Belmont water measures 37 mg/L (2.2 gpg) of hardness, soft by USGS standards. The number comes from California Water Service - San Mateo, dated October 2025.

Belmont on the hardness scale, with nearby cities
060120180240300360+CA typical 121Burlingame: 31 mg/LBurlingame 31Redwood City: 32 mg/LRedwood City 32North Fair Oaks: 32 mg/LNorth Fair Oaks 32Woodside: 32 mg/LWoodside 32San Carlos: 33 mg/LSan Carlos 33Foster City: 33 mg/LFoster City 33San Mateo: 35 mg/LSan Mateo 35Hillsborough: 36 mg/LHillsborough 36Millbrae: 44 mg/LMillbrae 44Menlo Park: 46 mg/LMenlo Park 46Belmont 37mg/L as calcium carbonate060120180240300360+CA 121Redwood City: 32 mg/LRedwood Ci. 32North Fair Oaks: 32 mg/LNorth Fair. 32San Carlos: 33 mg/LSan Carlos 33Foster City: 33 mg/LFoster City 33San Mateo: 35 mg/LSan Mateo 35Hillsborough: 36 mg/LHillsborou. 3637 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 37 mg/L, Belmont is 84 mg/L below the typical California figure of 121. Of the 10 nearest cities we track, 8 have softer water and 2 have harder. The range nearby runs from 31 mg/L in Burlingame to 46 in Menlo Park.

What 37 mg/L means at home

Soap and shampoo lather with very little product. Kettles and showerheads stay mostly free of white crust.

Some people notice that soap feels slow to rinse off in soft water. That slippery feel is normal and harmless.

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

Nothing, as far as hardness goes. At 37 mg/L a softener would have almost nothing to remove.

Carbon filter

If the water tastes of chlorine, a pitcher or faucet carbon filter takes care of that. It does not change hardness.

EPA record for Belmont's water system

California Water Service - San Mateo · PWSID CA4110008

No health-based violations since 2016

Serves about 103,536 people from surface water.

Health-based
0
Monitoring or reporting
0
Open now
0

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

No. It measures about 37 mg/L (2.2 grains per gallon), which the USGS classes as soft.

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

About 2.2 gpg. One grain per gallon equals 17.1 mg/L, so 37 mg/L divided by 17.1 gives 2.2.

Has the Belmont water system had EPA violations?

EPA records show no health-based violations for California Water Service - San Mateo since 2016.

Nearby cities

All 515 cities in California

Hardness data: TapWaterData US Water Hardness (utility report, October 14, 2025), CC BY 4.0. Population: US Census Bureau. Violations: EPA ECHO. How we use them.