Hard water in Mandan, ND
County estimate from 348 water samples in Morton County · July 2026
- ND typical
- 133 mg/L
- EPA health violations since 2016
- 0
- Softener for 3 people
- 32k grain
- Data
- County estimate
Water samples from around Mandan put hardness at about 337 mg/L (19.7 gpg), which would be very hard on the USGS scale. Treat this as a rough guide: it is the median of 348 samples taken across Morton County, mostly wells and streams, not a test of Mandan's treated tap water. One more reason for caution: EPA lists Mandan's water system as using surface water, which is often softer than the wells behind the county figure.
Mandan sits 204 mg/L above the typical North Dakota figure of 133. Of the 5 nearest cities we track, 3 have softer water and 2 have harder. The range nearby runs from 79 mg/L in Fargo to 392 in West Fargo.
What 337 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 337 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 × 19.7 gpg = 4,435 grains a day. A 32,000-grain unit regenerates about every 7 days.
EPA record for Mandan's water system
No health-based violations since 2016
Serves about 21,769 people from surface water.
- Health-based
- 0
- Monitoring or reporting
- 0
- Open now
- 0
EPA lists this system as serving Mandan.
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 Mandan water hard?
Yes. It measures about 337 mg/L (19.7 grains per gallon), which the USGS classes as very hard.
What is the water hardness in Mandan in grains per gallon?
About 19.7 gpg. One grain per gallon equals 17.1 mg/L, so 337 mg/L divided by 17.1 gives 19.7.
What size water softener do I need in Mandan?
For 3 people using 75 gallons each per day, 19.7 gpg works out to about 4,435 grains a day. A 32,000-grain softener covers that with a regeneration about every 7 days.
Has the Mandan water system had EPA violations?
EPA records show no health-based violations for Mandan City of since 2016.
Nearby cities
- Bismarck133 mg/LHard
- Dickinson320 mg/LVery hard
- West Fargo392 mg/LVery hard
- Fargo79 mg/LModerately hard
- Grand Forks390 mg/LVery hard
Hardness data: TapWaterData US Water Hardness (county estimate, July 4, 2026), CC BY 4.0. Population: US Census Bureau. Violations: EPA ECHO. How we use them.