Half Moon Bay, CA water hardness

Tap water hardness
46mg/L
2.7gpg
SoftReports range 30–46

Reported by Coastside County Water District · July 2025

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

Tap water in Half Moon Bay has about 46 mg/L of hardness, which is 2.7 grains per gallon. On the USGS scale that counts as soft. The number comes from Coastside County Water District, dated July 2025. Reports for this system disagree, with values from 30 to 46 mg/L.

Half Moon Bay on the hardness scale, with nearby cities
060120180240300360+CA typical 121Burlingame: 31 mg/LBurlingame 31Woodside: 32 mg/LWoodside 32San Carlos: 33 mg/LSan Carlos 33San Mateo: 35 mg/LSan Mateo 35Hillsborough: 36 mg/LHillsborough 36Belmont: 37 mg/LBelmont 37Millbrae: 44 mg/LMillbrae 44San Bruno: 44 mg/LSan Bruno 44El Granada: 46 mg/LEl Granada 46Pacifica: 70 mg/LPacifica 70Half Moon Bay 46mg/L as calcium carbonate060120180240300360+CA 121Burlingame: 31 mg/LBurlingame 31San Mateo: 35 mg/LSan Mateo 35Hillsborough: 36 mg/LHillsborou. 36Belmont: 37 mg/LBelmont 37Millbrae: 44 mg/LMillbrae 44El Granada: 46 mg/LEl Granada 4646 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 46 mg/L, Half Moon Bay is 75 mg/L below the typical California figure of 121. Of the 10 nearest cities we track, 8 have softer water and 1 has harder. The range nearby runs from 31 mg/L in Burlingame to 70 in Pacifica.

What 46 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 46 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 Half Moon Bay's water system

Coastside County Water District · PWSID CA4110011

No health-based violations since 2016

Serves about 19,033 people from surface water.

Health-based
0
Monitoring or reporting
0
Open now
0

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 Half Moon Bay water hard?

No. It measures about 46 mg/L (2.7 grains per gallon), which the USGS classes as soft.

What is the water hardness in Half Moon Bay in grains per gallon?

About 2.7 gpg. One grain per gallon equals 17.1 mg/L, so 46 mg/L divided by 17.1 gives 2.7.

Has the Half Moon Bay water system had EPA violations?

EPA records show no health-based violations for Coastside County Water District since 2016.

Nearby cities

All 515 cities in California

Hardness data: TapWaterData US Water Hardness (utility report, July 9, 2025), CC BY 4.0. Population: US Census Bureau. Violations: EPA ECHO. How we use them.