Mill Valley, CA water hardness

Tap water hardness
56mg/L
3.3gpg
Soft

Reported by Marin Municipal Water District · October 2025

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

Mill Valley water measures 56 mg/L (3.3 gpg) of hardness, soft by USGS standards. The number comes from Marin Municipal Water District, dated October 2025.

Mill Valley on the hardness scale, with nearby cities
060120180240300360+CA typical 121Tamalpais-Homestead Valley: 56 mg/LTamalpais-Homestead Valley 56Kentfield: 56 mg/LKentfield 56Strawberry: 56 mg/LStrawberry 56Larkspur: 56 mg/LLarkspur 56Corte Madera: 56 mg/LCorte Madera 56Sausalito: 56 mg/LSausalito 56Tiburon: 56 mg/LTiburon 56San Anselmo: 56 mg/LSan Anselmo 56San Rafael: 56 mg/LSan Rafael 56Fairfax: 56 mg/LFairfax 56Mill Valley 56mg/L as calcium carbonate060120180240300360+CA 121Tamalpais-Homestead Valley: 56 mg/LTamalpais-. 56Kentfield: 56 mg/LKentfield 56Strawberry: 56 mg/LStrawberry 56Larkspur: 56 mg/LLarkspur 56Corte Madera: 56 mg/LCorte Made. 56Sausalito: 56 mg/LSausalito 5656 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 56 mg/L, Mill Valley is 65 mg/L below the typical California figure of 121. None of the 10 nearest cities we track has harder water.

What 56 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 56 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 Mill Valley's water system

Marin Municipal Water District · PWSID CA2110002

No health-based violations since 2016

Serves about 188,116 people from surface water.

Health-based
0
Monitoring or reporting
0
Open now
0

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

No. It measures about 56 mg/L (3.3 grains per gallon), which the USGS classes as soft.

What is the water hardness in Mill Valley in grains per gallon?

About 3.3 gpg. One grain per gallon equals 17.1 mg/L, so 56 mg/L divided by 17.1 gives 3.3.

Has the Mill Valley water system had EPA violations?

EPA records show no health-based violations for Marin Municipal Water District since 2016.

Nearby cities

All 515 cities in California

Hardness data: TapWaterData US Water Hardness (utility report, October 6, 2025), CC BY 4.0. Population: US Census Bureau. Violations: EPA ECHO. How we use them.