How hard is the water in Brentwood, CA?

Tap water hardness
86mg/L
5.1gpg
Moderately hard

Reported by Contra Costa Water District · October 2025

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

Brentwood water measures 86 mg/L (5.1 gpg) of hardness, moderately hard by USGS standards. The number comes from Contra Costa Water District, dated October 2025.

Brentwood on the hardness scale, with nearby cities
060120180240300360+CA typical 121Camino Tassajara: 34 mg/LCamino Tassajara 34Blackhawk: 34 mg/LBlackhawk 34Mountain House: 61 mg/LMountain House 61Antioch: 82 mg/LAntioch 82Pittsburg: 82 mg/LPittsburg 82Clayton: 86 mg/LClayton 86Concord: 86 mg/LConcord 86Bay Point: 88 mg/LBay Point 88Oakley: 89 mg/LOakley 89Discovery Bay: 137 mg/LDiscovery Bay 137Brentwood 86mg/L as calcium carbonate060120180240300360+CA 121Camino Tassajara: 34 mg/LCamino Tas. 34Antioch: 82 mg/LAntioch 82Pittsburg: 82 mg/LPittsburg 82Clayton: 86 mg/LClayton 86Oakley: 89 mg/LOakley 89Discovery Bay: 137 mg/LDiscovery. 13786 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 86 mg/L, Brentwood is 35 mg/L below the typical California figure of 121. Of the 10 nearest cities we track, 5 have softer water and 3 have harder. The range nearby runs from 34 mg/L in Camino Tassajara to 137 in Discovery Bay.

What 86 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 Brentwood

3 people × 75 gallons a day × 5.1 gpg = 1,138 grains a day. A 24,000-grain unit regenerates about every 21 days.

Size it for your household

EPA record for Brentwood's water system

Brentwood · PWSID CA0710004

No health-based violations since 2016

Serves about 64,513 people from surface water.

Health-based
0
Monitoring or reporting
0
Open now
0

EPA lists Brentwood as the system serving Brentwood. The hardness figure above comes from a different system's report, which TapWaterData uses for Brentwood.

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 Brentwood water hard?

Somewhat. It measures about 86 mg/L (5.1 grains per gallon), which the USGS classes as moderately hard.

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

About 5.1 gpg. One grain per gallon equals 17.1 mg/L, so 86 mg/L divided by 17.1 gives 5.1.

What size water softener do I need in Brentwood?

For 3 people using 75 gallons each per day, 5.1 gpg works out to about 1,138 grains a day. A 24,000-grain softener covers that with a regeneration about every 21 days.

Has the Brentwood water system had EPA violations?

EPA records show no health-based violations for Brentwood since 2016.

Nearby cities

All 515 cities in California

Hardness data: TapWaterData US Water Hardness (utility report, October 1, 2025), CC BY 4.0. Population: US Census Bureau. Violations: EPA ECHO. How we use them.