How hard is the water in Lucas Valley-Marinwood, CA?

Tap water hardness
63mg/L
3.7gpg
Moderately hard

Reported by Marin Municipal Water District · October 2025

CA typical
121 mg/L
EPA health violations since 2016
0
Softener for 3 people
24k grain
Data
Utility report

The water in Lucas Valley-Marinwood carries roughly 63 mg/L of dissolved calcium and magnesium, or 3.7 grains per gallon. That is moderately hard water. The number comes from Marin Municipal Water District, dated October 2025.

Lucas Valley-Marinwood on the hardness scale, with nearby cities
060120180240300360+CA typical 121Fairfax: 56 mg/LFairfax 56San Anselmo: 56 mg/LSan Anselmo 56San Rafael: 56 mg/LSan Rafael 56Kentfield: 56 mg/LKentfield 56Larkspur: 56 mg/LLarkspur 56Corte Madera: 56 mg/LCorte Madera 56Mill Valley: 56 mg/LMill Valley 56Strawberry: 56 mg/LStrawberry 56Tamalpais-Homestead Valley: 56 mg/LTamalpais-Homestead Valley 56Novato: 63 mg/LNovato 63Lucas Valley-Marinwood 63mg/L as calcium carbonate060120180240300360+CA 121Fairfax: 56 mg/LFairfax 56San Anselmo: 56 mg/LSan Anselmo 56San Rafael: 56 mg/LSan Rafael 56Kentfield: 56 mg/LKentfield 56Larkspur: 56 mg/LLarkspur 56Novato: 63 mg/LNovato 6363 mg/Lmg/L as calcium carbonate
Soft 0–60 mg/LModerately hard 61–120 mg/LHard 121–180 mg/LVery hard 181+ mg/L

Lucas Valley-Marinwood sits 58 mg/L below the typical California figure of 121. None of the 10 nearest cities we track has harder water. The range nearby runs from 56 mg/L in Fairfax to 63 in Novato.

What 63 mg/L means at home

You may see faint white spots on glasses and shower doors after the water dries.

Scale builds up slowly. A kettle or coffee maker needs descaling now and then, maybe every few months.

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

Optional. Plenty of households at this level live with it and descale the kettle now and then.

Water softener

Worth a look if spots on glass bother you, or if your tankless water heater manual asks for softer water.

Carbon filter

Improves taste and removes chlorine. It leaves calcium and magnesium in place.

Softener size for Lucas Valley-Marinwood

3 people × 75 gallons a day × 3.7 gpg = 828 grains a day. A 24,000-grain unit regenerates about every 28 days.

Size it for your household

EPA record for Lucas Valley-Marinwood'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 Lucas Valley-Marinwood to this system. EPA's service-area records do not name Lucas Valley-Marinwood, 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 Lucas Valley-Marinwood water hard?

Somewhat. It measures about 63 mg/L (3.7 grains per gallon), which the USGS classes as moderately hard.

What is the water hardness in Lucas Valley-Marinwood in grains per gallon?

About 3.7 gpg. One grain per gallon equals 17.1 mg/L, so 63 mg/L divided by 17.1 gives 3.7.

What size water softener do I need in Lucas Valley-Marinwood?

For 3 people using 75 gallons each per day, 3.7 gpg works out to about 828 grains a day. A 24,000-grain softener covers that with a regeneration about every 28 days.

Has the Lucas Valley-Marinwood 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.