Hard water in St. Petersburg, FL
Reported by Pinellas County Utilities · October 2025
- FL typical
- 120 mg/L
- EPA health violations since 2016
- 0
- Softener for 3 people
- 24k grain
- Data
- Utility report
Tap water in St. Petersburg has about 129 mg/L of hardness, which is 7.6 grains per gallon. On the USGS scale that counts as hard. The number comes from Pinellas County Utilities, dated October 2025.
At 129 mg/L, St. Petersburg is close to the typical Florida figure of 120 mg/L. None of the 10 nearest cities we track has softer water. The range nearby runs from 129 mg/L in Gulfport to 141 in Apollo Beach.
What 129 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 129 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 × 7.6 gpg = 1,701 grains a day. A 24,000-grain unit regenerates about every 14 days.
EPA record for St. Petersburg's water system
No health-based violations since 2016
Serves about 349,979 people from surface water.
- Health-based
- 0
- Monitoring or reporting
- 9
- Open now
- 0
EPA lists ST Petersburg, City of as the system serving St. Petersburg. The hardness figure above comes from a different system's report, which TapWaterData uses for St. Petersburg.
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 St. Petersburg water hard?
Yes. It measures about 129 mg/L (7.6 grains per gallon), which the USGS classes as hard.
What is the water hardness in St. Petersburg in grains per gallon?
About 7.6 gpg. One grain per gallon equals 17.1 mg/L, so 129 mg/L divided by 17.1 gives 7.6.
What size water softener do I need in St. Petersburg?
For 3 people using 75 gallons each per day, 7.6 gpg works out to about 1,701 grains a day. A 24,000-grain softener covers that with a regeneration about every 14 days.
Has the St. Petersburg water system had EPA violations?
EPA records show no health-based violations for ST Petersburg, City of since 2016. There were also 9 monitoring or reporting violations, which are about late or missing tests and notices.
Nearby cities
- Gulfport129 mg/LHard
- Lealman129 mg/LHard
- South Pasadena133 mg/LHard
- West Lealman129 mg/LHard
- Treasure Island133 mg/LHard
- Pinellas Park133 mg/LHard
- Bardmoor133 mg/LHard
- Seminole133 mg/LHard
- Largo133 mg/LHard
- Apollo Beach141 mg/LHard
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.