Hard water in Seaside, CA
Reported by Cal Am Water Company - Monterey · September 2025
- CA typical
- 121 mg/L
- EPA health violations since 2016
- 0
- Softener for 3 people
- 24k grain
- Data
- Utility report
Seaside water measures 160 mg/L (9.3 gpg) of hardness, hard by USGS standards. The number comes from Cal Am Water Company - Monterey, dated September 2025.
At 160 mg/L, Seaside is 39 mg/L above the typical California figure of 121. Of the 10 nearest cities we track, 6 have softer water and 3 have harder. The range nearby runs from 98 mg/L in Rio del Mar to 215 in Watsonville.
What 160 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 160 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.
3 people × 75 gallons a day × 9.3 gpg = 2,102 grains a day. A 24,000-grain unit regenerates about every 11 days.
EPA record for Seaside's water system
No health-based violations since 2016
Serves about 128,928 people from surface water.
- Health-based
- 0
- Monitoring or reporting
- 0
- Open now
- 0
TapWaterData ties Seaside to this system. EPA's service-area records do not name Seaside, 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 Seaside water hard?
Yes. It measures about 160 mg/L (9.3 grains per gallon), which the USGS classes as hard.
What is the water hardness in Seaside in grains per gallon?
About 9.3 gpg. One grain per gallon equals 17.1 mg/L, so 160 mg/L divided by 17.1 gives 9.3.
What size water softener do I need in Seaside?
For 3 people using 75 gallons each per day, 9.3 gpg works out to about 2,102 grains a day. A 24,000-grain softener covers that with a regeneration about every 11 days.
Has the Seaside water system had EPA violations?
EPA records show no health-based violations for Cal Am Water Company - Monterey since 2016.
Nearby cities
- Monterey160 mg/LHard
- Marina142 mg/LHard
- Pacific Grove169 mg/LHard
- Salinas106 mg/LModerately hard
- Watsonville215 mg/LVery hard
- Interlaken215 mg/LVery hard
- Rio del Mar98 mg/LModerately hard
- Pleasure Point132 mg/LHard
- Capitola132 mg/LHard
- Aptos98 mg/LModerately hard
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.