Rio Vista, CA water hardness

Tap water hardness
49mg/L
2.9gpg
Soft

Reported by City of Rio Vista · March 2025

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

Rio Vista water measures 49 mg/L (2.9 gpg) of hardness, soft by USGS standards. The number comes from City of Rio Vista, dated March 2025.

Rio Vista on the hardness scale, with nearby cities
060120180240300360+CA typical 121Antioch: 82 mg/LAntioch 82Pittsburg: 82 mg/LPittsburg 82Brentwood: 86 mg/LBrentwood 86Bay Point: 88 mg/LBay Point 88Oakley: 89 mg/LOakley 89Vacaville: 94 mg/LVacaville 94Suisun City: 107 mg/LSuisun City 107Fairfield: 109 mg/LFairfield 109Discovery Bay: 137 mg/LDiscovery Bay 137Dixon: 152 mg/LDixon 152Rio Vista 49mg/L as calcium carbonate060120180240300360+CA 121Antioch: 82 mg/LAntioch 82Pittsburg: 82 mg/LPittsburg 82Brentwood: 86 mg/LBrentwood 86Bay Point: 88 mg/LBay Point 88Oakley: 89 mg/LOakley 89Suisun City: 107 mg/LSuisun City 10749 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 49 mg/L, Rio Vista is 72 mg/L below the typical California figure of 121. None of the 10 nearest cities we track has softer water. The range nearby runs from 82 mg/L in Antioch to 152 in Dixon.

What 49 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 49 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 Rio Vista's water system

City of Rio Vista · PWSID CA4810004

No health-based violations since 2016

Serves about 11,206 people from groundwater.

Health-based
0
Monitoring or reporting
1
Open now
1

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 Rio Vista water hard?

No. It measures about 49 mg/L (2.9 grains per gallon), which the USGS classes as soft.

What is the water hardness in Rio Vista in grains per gallon?

About 2.9 gpg. One grain per gallon equals 17.1 mg/L, so 49 mg/L divided by 17.1 gives 2.9.

Has the Rio Vista water system had EPA violations?

EPA records show no health-based violations for City of Rio Vista since 2016. There were also 1 monitoring or reporting violation, which are about late or missing tests and notices.

Nearby cities

All 515 cities in California

Hardness data: TapWaterData US Water Hardness (utility report, March 11, 2025), CC BY 4.0. Population: US Census Bureau. Violations: EPA ECHO. How we use them.