Hard water in Ann Arbor, MI
Reported by Ann Arbor · October 2025
- MI typical
- 112 mg/L
- EPA health violations since 2016
- 0
- Softener for 3 people
- 24k grain
- Data
- Utility report
Tap water in Ann Arbor has about 156 mg/L of hardness, which is 9.1 grains per gallon. On the USGS scale that counts as hard. The number comes from Ann Arbor, dated October 2025. Reports for this system disagree, with values from 126 to 156 mg/L.
Ann Arbor sits 44 mg/L above the typical Michigan figure of 112. Of the 10 nearest cities we track, 6 have softer water and 4 have harder. The range nearby runs from 91 mg/L in Wayne to 460 in South Lyon.
What 156 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 156 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 × 9.1 gpg = 2,052 grains a day. A 24,000-grain unit regenerates about every 11 days.
EPA record for Ann Arbor's water system
No health-based violations since 2016
Serves about 123,851 people from surface water.
- Health-based
- 0
- Monitoring or reporting
- 2
- Open now
- 1
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 Ann Arbor water hard?
Yes. It measures about 156 mg/L (9.1 grains per gallon), which the USGS classes as hard.
What is the water hardness in Ann Arbor in grains per gallon?
About 9.1 gpg. One grain per gallon equals 17.1 mg/L, so 156 mg/L divided by 17.1 gives 9.1.
What size water softener do I need in Ann Arbor?
For 3 people using 75 gallons each per day, 9.1 gpg works out to about 2,052 grains a day. A 24,000-grain softener covers that with a regeneration about every 11 days.
Has the Ann Arbor water system had EPA violations?
EPA records show no health-based violations for Ann Arbor since 2016. There were also 2 monitoring or reporting violations, which are about late or missing tests and notices.
Nearby cities
- Ypsilanti168 mg/LHard
- Saline123 mg/LHard
- Whitmore Lake184 mg/LVery hard
- South Lyon460 mg/LVery hard
- Plymouth104 mg/LModerately hard
- Northville132 mg/LHard
- Wayne91 mg/LModerately hard
- Brighton418 mg/LVery hard
- Westland96 mg/LModerately hard
- Novi116 mg/LModerately hard
Hardness data: TapWaterData US Water Hardness (utility report, October 13, 2025), CC BY 4.0. Population: US Census Bureau. Violations: EPA ECHO. How we use them.