WaterProfile Local

Utilities / Michigan

Ann Arbor, MI water hardness

City of Ann Arbor Water Treatment Services publishes an average hardness of 126 mg/L (7.4 grains per gallon, also its own figure) for its system, in its City of Ann Arbor 2025 Water Quality Report. On the USGS scale that is hard water, though the utility's own range crosses more than one class — it spans moderately hard and hard water from end to end.

Soft Moderate Hard Very hard 0 60 120 180 500+ 126 mg/L Ann Arbor, MI sits in the hard band mg/L as CaCO₃. Bands drawn equal width, so the axis is not linear.
City of Ann Arbor Water Treatment Services published an average of 126 mg/L, with a published range of 74 to 180 mg/L shown as the bar. The plotted point is the published average. Classification bands from the USGS Water Science School.

The published figure, exactly as it appears

This is the hardness line transcribed from the source, with nothing added:

Hardness (ppm as CaCO3) 126 74 - 180 […] Hardness (gpg as CaCO3) 7.4 4.3 - 10.5

City of Ann Arbor Water Treatment Services, City of Ann Arbor 2025 Water Quality Report

Units as published: ppm as CaCO3 and gpg as CaCO3. What kind of figure it is: an average with a range. Retrieved 2026-10-17.

Ann Arbor hardness in mg/L and grains per gallon

Water-quality reports use mg/L (identical to ppm). Softener instructions and plumbing specifications use grains per gallon. Both are below. Where a figure is our arithmetic rather than the utility's own number, it says so.

Figuremg/L (ppm)Grains per gallonWhose number
Published average1267.4both published by the utility
Low end of published range744.3both published by the utility
High end of published range18010.5both published by the utility
Plotted on the scale above1267.4published average; the gpg here is our conversion at 17.1, so it can differ slightly from a utility’s own rounded gpg figure

The conversion, both ways: gpg = mg/L ÷ 17.1 and mg/L = gpg × 17.1. Worked for this system: 126 ÷ 17.1 = 7.4 gpg. The converter does °dH and °f as well, and why the factor is 17.1 explains where the number comes from.

What this figure does not tell you

Service area and source water

UtilityCity of Ann Arbor Water Treatment Services
Service area as publishedThe City of Ann Arbor's water system. The report does not break hardness down by source.

Provenance of every number on this page

Source documentCity of Ann Arbor 2025 Water Quality Report
Source URLhttps://www.a2gov.org/media/ibsanbbm/ann-arbor-water-2025-consumer-confidence-report.pdf
Published byCity of Ann Arbor Water Treatment Services
Report year2025
Year noteCovers January 1 to December 31, 2025. The hardness rows are in the report's “Other Water Quality Parameters of Interest” table, under its “Average Level Detected” and “Results Range” columns.
Retrieved2026-10-17
Classification bandsUSGS Water Science School, retrieved 2026-10-16

Notes the report forces on this page

If you are sizing a softener for Ann Arbor water

At 7.4 gpg, the sizing arithmetic starts from your household's water use, not from the hardness alone. The calculator below is pre-filled with this system's figure and every other input is an editable assumption.

Whether a softener is worth installing at this hardness is a judgement, not arithmetic, and it is not one this site makes for you. Nothing here has been tested by the author.

Where Ann Arbor sits against other verified systems

Soft Soft 0–60
Moderately hard Moderate 61–120
Hard Hard 121–180
Very hard Very hard 181+
  1. Portland, OR 9 mg/L 0.5 gpg Soft
  2. Boston, MA 16 mg/L 1 gpg Soft
  3. Manchester, NH 17.9 mg/L 1 gpg Soft
  4. Raleigh, NC 25 mg/L 1.47 gpg Soft
  5. New York, NY 32 mg/L 2 gpg Soft
  6. Charlotte, NC 32 mg/L 1.9 gpg Soft
  7. Memphis, TN 46 mg/L 2.7 gpg Soft
  8. Anchorage, AK 56 mg/L 3.3 gpg Soft
  9. Oakland, CA 68.4 mg/L 4 gpg Moderately hard
  10. Nashville, TN 77.3 mg/L 4.5 gpg Moderately hard
  11. Sacramento, CA 83 mg/L 4.9 gpg Moderately hard
  12. Fresno, CA 89.3 mg/L 5.2 gpg Moderately hard
  13. Saint Paul, MN 90 mg/L 5 gpg Moderately hard
  14. Austin, TX 93 mg/L 5.4 gpg Moderately hard
  15. Washington, DC 95 mg/L 5.6 gpg Moderately hard
  16. Birmingham, AL 98 mg/L 5.7 gpg Moderately hard
  17. Kansas City, MO 100 mg/L 5.8 gpg Moderately hard
  18. Denver, CO 105 mg/L 6.1 gpg Moderately hard
  19. Tulsa, OK 114.5 mg/L 6.7 gpg Moderately hard
  20. Louisville, KY 115 mg/L 6.7 gpg Moderately hard
  21. Columbus, OH 120 mg/L 7 gpg Moderately hard
  22. Cleveland, OH 120 mg/L 7 gpg Moderately hard
  23. Philadelphia, PA 125 mg/L 7.3 gpg Hard
  24. Ann Arbor, MI 126 mg/L 7.4 gpg Hard
  25. Cincinnati, OH 133 mg/L 7.8 gpg Hard
  26. Milwaukee, WI 137 mg/L 8.01 gpg Hard
  27. St. Louis, MO 138 mg/L 8.1 gpg Hard
  28. Fort Worth, TX 145 mg/L 8.5 gpg Hard
  29. Honolulu, HI 162.5 mg/L 9.5 gpg Hard
  30. Wichita, KS 170 mg/L 9.9 gpg Hard
  31. Omaha, NE 170 mg/L 10 gpg Hard
  32. Los Angeles, CA 192 mg/L 11.2 gpg Very hard
  33. Lincoln, NE 192 mg/L 11.2 gpg Very hard
  34. Tampa, FL 220 mg/L 12.9 gpg Very hard
  35. Phoenix, AZ 237 mg/L 13.9 gpg Very hard
  36. Mesa, AZ 239.4 mg/L 14 gpg Very hard
  37. San Diego, CA 276 mg/L 16 gpg Very hard
  38. Las Vegas, NV 280 mg/L 16 gpg Very hard
  39. Chandler, AZ 282.2 mg/L 16.5 gpg Very hard
  40. San Antonio, TX 299.3 mg/L 17.5 gpg Very hard
  41. Anaheim, CA 300 mg/L 18 gpg Very hard
  42. Indianapolis, IN 317 mg/L 19 gpg Very hard
  43. Madison, WI 324.9 mg/L 19 gpg Very hard
  44. Scottsdale, AZ 352.5 mg/L 20.6 gpg Very hard

mg/L as calcium carbonate. Each classification band is drawn the same width, so the axis is not linear in mg/L.

Ann Arbor, MI is the highlighted row. Every other system on this chart has its own page with its own published figure and report date. Grains per gallon are the utility's own figure where it published one, and our conversion at 17.1 mg/L per grain where it did not.

Systems with similar published hardness

All 44 verified systems   How to find hardness in your own utility's report   If you are on a well instead