Hard water in Pomona, CA

Tap water hardness
138mg/L
8.1gpg
Hard

Reported by Pomona - City, Water Dept. · September 2025

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

The water in Pomona carries roughly 138 mg/L of dissolved calcium and magnesium, or 8.1 grains per gallon. That is hard water. The number comes from Pomona - City, Water Dept., dated September 2025.

Pomona on the hardness scale, with nearby cities
060120180240300360+CA typical 121Glendora: 122 mg/LGlendora 122Upland: 126 mg/LUpland 126Diamond Bar: 153 mg/LDiamond Bar 153Claremont: 157 mg/LClaremont 157Montclair: 166 mg/LMontclair 166Covina: 167 mg/LCovina 167Walnut: 210 mg/LWalnut 210La Verne: 231 mg/LLa Verne 231San Dimas: 275 mg/LSan Dimas 275Charter Oak: 275 mg/LCharter Oak 275Pomona 138mg/L as calcium carbonate060120180240300360+CA 121Diamond Bar: 153 mg/LDiamond Bar 153Claremont: 157 mg/LClaremont 157Montclair: 166 mg/LMontclair 166Walnut: 210 mg/LWalnut 210La Verne: 231 mg/LLa Verne 231San Dimas: 275 mg/LSan Dimas 275138 mg/Lmg/L as calcium carbonate
Soft 0–60 mg/LModerately hard 61–120 mg/LHard 121–180 mg/LVery hard 181+ mg/L

Pomona sits 17 mg/L above the typical California figure of 121. Of the 10 nearest cities we track, 2 have softer water and 8 have harder. The range nearby runs from 122 mg/L in Glendora to 275 in San Dimas.

What 138 mg/L means at home

Expect white crust on faucets and showerheads, plus spots on dishes that come out of the dishwasher.

Kettles collect scale quickly. Water heaters build up sediment at the bottom of the tank, which makes them work harder over time.

Soap and detergent need a little more to lather, and soap scum shows up in the tub.

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

At 138 mg/L most of the trouble is scale, and only a few things deal with it.

Ion-exchange water softener

The standard whole-house fix. It swaps calcium and magnesium for sodium or potassium and needs salt plus a drain. Size it with the calculator below.

Salt-free conditioner

No salt and no drain line. It changes how minerals form scale instead of removing them, so water still tests hard.

Reverse osmosis or carbon filter

Under-sink reverse osmosis removes minerals from drinking water only. Plain carbon filters improve taste but do not soften.

Softener size for Pomona

3 people × 75 gallons a day × 8.1 gpg = 1,822 grains a day. A 24,000-grain unit regenerates about every 13 days.

Size it for your household

EPA record for Pomona's water system

Pomona - City, Water Dept. · PWSID CA1910126

No health-based violations since 2016

Serves about 151,713 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 Pomona water hard?

Yes. It measures about 138 mg/L (8.1 grains per gallon), which the USGS classes as hard.

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

About 8.1 gpg. One grain per gallon equals 17.1 mg/L, so 138 mg/L divided by 17.1 gives 8.1.

What size water softener do I need in Pomona?

For 3 people using 75 gallons each per day, 8.1 gpg works out to about 1,822 grains a day. A 24,000-grain softener covers that with a regeneration about every 13 days.

Has the Pomona water system had EPA violations?

EPA records show no health-based violations for Pomona - City, Water Dept. since 2016.

Nearby cities

All 515 cities in California

Hardness data: TapWaterData US Water Hardness (utility report, September 29, 2025), CC BY 4.0. Population: US Census Bureau. Violations: EPA ECHO. How we use them.