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How to test your water hardness at home
On city water, start with your utility's report. If you want your own number, a drop-count titration kit gives you grains per gallon directly; strips only place you in a range, TDS pens don't measure hardness at all, and private wells should go to a certified lab.
First: you may not need to test
If you're on a public water system, your utility already measures hardness and usually publishes it in its annual water quality report. EPA WaterSense suggests finding your hardness from that report or by having a professional test your water before you buy a softener. See how to find hardness in your water report.
Testing your own tap is still useful if the report gives a wide range, if you're on a private well, or if you want to check that a softener is actually working.
Your options, from rough to precise
Test strips
You dip a strip and match its color to a printed chart. The chart has a handful of color bands, so the result is a range (for example "hard" or "very hard"), not an exact number. That's fine for a quick yes-or-no check, such as whether softened water is coming out soft. It's a weak basis for sizing a softener or setting its hardness dial, because those settings use a specific grains-per-gallon figure (sizing math here).
Drop-count titration kits
These kits add an indicator that turns the sample pink or red when hardness is present, then you add a titrating solution one drop at a time until it turns blue. With Hach's Model 5-B kit, for example, the manufacturer says each drop equals 1 grain per gallon (17.1 mg/L as CaCO3), the range is 1–30 gpg, and it measures total hardness (calcium plus magnesium). Counting drops gives you a number you can plug straight into a softener's settings. In public r/WaterTreatment threads, this type of kit is the usual recommendation when someone asks how to get a better number than strips give.
[Affiliate link pending] Drop-count total hardness test kit
TDS meters (skip them for hardness)
A TDS pen reads total dissolved solids, which CDC describes as how much "stuff" (for example, calcium or sodium) is mixed into the water. Hardness is only the calcium and magnesium part of that. A standard softener swaps calcium and magnesium for sodium (or potassium), as EPA WaterSense explains, so the dissolved-solids total doesn't drop the way hardness does. A TDS reading can't tell you your hardness or whether the softener is working.
Certified lab test
A lab test reports hardness (and often calcium, magnesium, iron and manganese separately) in mg/L. EPA advises using only laboratories certified for drinking water testing. This is the right choice for private wells, discussed below.
[Affiliate link pending] Mail-in lab water test
Getting a clean reading
- Use the cold tap. Hot water has passed through the water heater, where scale can settle out.
- Know which water you're sampling. If you have a softener, kitchen and bathroom taps are usually softened. To read your incoming hardness, use a tap that bypasses it (often an outdoor spigot) or put the softener in bypass first. Test both if you want to see what the softener removes.
- Convert units before comparing. Kits may report gpg while reports use mg/L or ppm. Divide mg/L by about 17.1 to get gpg (units explained).
- Check iron too if you're buying a softener. EPA's well-testing chart pairs "water softener needed to treat hardness" with testing for manganese and iron.
Private wells: hardness isn't the first test
EPA rules for public water systems don't cover private wells, so the owner is responsible for testing. CDC and EPA both say to test a private well at least once a year for total coliform bacteria, nitrates, total dissolved solids and pH, and to ask your local health department what else is common in your area. EPA's chart lists hardness as the test for "scaly residues, soaps don't lather."
In Ohio, Ohio EPA doesn't test private wells, but it certifies labs and publishes a combined list of them; it also suggests calling your local health department first, since it regulates private wells and may run a testing program. Ohio State's Ohioline fact sheet notes that Ohio has about 1 million homes on private wells.
Next step
Once you have a number, use the decision guide to see whether you need a softener at all, then size it.
Sources
- EPA WaterSense, Guide to Selecting and Maintaining a Water-Efficient Water Softener (2026, PDF)
- Hach, “Total Hardness Test Kit, Model 5-B (145300)” product page
- CDC, “Guidelines for Testing Well Water” (2024)
- EPA, “Protect Your Home's Water”
- Ohio EPA, “Testing water from private wells”
- Ohio EPA, Combined Lab List (certified drinking water labs, PDF)
- Ohio State University Extension, “Where to Have Your Water Tested” (AEX-315)
- r/WaterTreatment, “Testing for water hardness” (public thread, 2025)
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