Hard water in South Pasadena, CA
Reported by City of South Pasadena · July 2025
- CA typical
- 121 mg/L
- EPA health violations since 2016
- 0
- Softener for 3 people
- 24k grain
- Data
- Utility report
Tap water in South Pasadena has about 128 mg/L of hardness, which is 7.5 grains per gallon. On the USGS scale that counts as hard. The number comes from City of South Pasadena, dated July 2025.
At 128 mg/L, South Pasadena is close to the typical California figure of 121 mg/L. Of the 10 nearest cities we track, 6 have softer water and 4 have harder. The range nearby runs from 34 mg/L in South San Gabriel to 230 in Pasadena.
What 128 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 128 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 × 7.5 gpg = 1,685 grains a day. A 24,000-grain unit regenerates about every 14 days.
EPA record for South Pasadena's water system
No health-based violations since 2016
Serves about 25,329 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 South Pasadena water hard?
Yes. It measures about 128 mg/L (7.5 grains per gallon), which the USGS classes as hard.
What is the water hardness in South Pasadena in grains per gallon?
About 7.5 gpg. One grain per gallon equals 17.1 mg/L, so 128 mg/L divided by 17.1 gives 7.5.
What size water softener do I need in South Pasadena?
For 3 people using 75 gallons each per day, 7.5 gpg works out to about 1,685 grains a day. A 24,000-grain softener covers that with a regeneration about every 14 days.
Has the South Pasadena water system had EPA violations?
EPA records show no health-based violations for City of South Pasadena since 2016.
Nearby cities
- Alhambra137 mg/LHard
- San Marino116 mg/LModerately hard
- San Gabriel116 mg/LModerately hard
- Pasadena230 mg/LVery hard
- East San Gabriel192 mg/LVery hard
- East Pasadena192 mg/LVery hard
- Rosemead46 mg/LSoft
- East Los Angeles123 mg/LHard
- South San Gabriel34 mg/LSoft
- Temple City113 mg/LModerately hard
Hardness data: TapWaterData US Water Hardness (utility report, July 22, 2025), CC BY 4.0. Population: US Census Bureau. Violations: EPA ECHO. How we use them.