Hard water in Miami, FL
Reported by Mdwasa/Rex Utilities · October 2025
- FL typical
- 120 mg/L
- EPA health violations since 2016
- 0
- Softener for 3 people
- 24k grain
- Data
- Utility report
The water in Miami carries roughly 248 mg/L of dissolved calcium and magnesium, or 14.5 grains per gallon. That is very hard water. The number comes from Mdwasa/Rex Utilities, dated October 2025.
Miami sits 128 mg/L above the typical Florida figure of 120. None of the 10 nearest cities we track has harder water. The range nearby runs from 20 mg/L in Miramar to 212 in Hialeah.
What 248 mg/L means at home
Scale forms fast here. Kettles and coffee makers need regular descaling, and showerheads clog unless you clean them.
Tank water heaters collect mineral sediment that insulates the water from the burner, so flushing the tank matters more than usual.
Dishes and glass shower doors spot easily. Soap scum and a dull film on hair or laundry are common complaints.
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 248 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 × 14.5 gpg = 3,258 grains a day. A 24,000-grain unit regenerates about every 7 days.
EPA record for Miami's water system
No health-based violations since 2016
Serves about 45,200 people from groundwater.
- Health-based
- 0
- Monitoring or reporting
- 14
- Open now
- 2
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 Miami water hard?
Yes. It measures about 248 mg/L (14.5 grains per gallon), which the USGS classes as very hard.
What is the water hardness in Miami in grains per gallon?
About 14.5 gpg. One grain per gallon equals 17.1 mg/L, so 248 mg/L divided by 17.1 gives 14.5.
What size water softener do I need in Miami?
For 3 people using 75 gallons each per day, 14.5 gpg works out to about 3,258 grains a day. A 24,000-grain softener covers that with a regeneration about every 7 days.
Has the Miami water system had EPA violations?
EPA records show no health-based violations for Mdwasa/Rex Utilities since 2016. There were also 14 monitoring or reporting violations, which are about late or missing tests and notices.
Nearby cities
- Miami Beach35 mg/LSoft
- Hialeah212 mg/LVery hard
- Surfside92 mg/LModerately hard
- North Miami89 mg/LModerately hard
- North Miami Beach212 mg/LVery hard
- Miami Gardens212 mg/LVery hard
- Country Club28 mg/LSoft
- Palm Springs North28 mg/LSoft
- Miramar20 mg/LSoft
- Hollywood51 mg/LSoft
Hardness data: TapWaterData US Water Hardness (utility report, October 3, 2025), CC BY 4.0. Population: US Census Bureau. Violations: EPA ECHO. How we use them.