What is a Good Water Hardness Number? July 28, 2020 13:06

What is a Good Water Hardness Number?

New to the numbers associated with hard water? Investigating the best water softener solutions can be confusing. We've made it easy - Here’s a breakdown of what you can expect to see in your water softener research and how to understand water quality in your own home.

What is Hard Water?

washing hands with hard waterThe simple definition of water hardness is the amount of dissolved calcium and magnesium in the water. Hard water is high in dissolved minerals, largely calcium and magnesium. You may have felt the effects of hard water, literally, the last time you washed your hands. Depending on the hardness of your water, after using soap to wash you may have felt like there was a film of residue left on your hands. In hard water, soap reacts with the calcium (which is relatively high in hard water) to form "soap scum". When using hard water, more soap or detergent is needed to get things clean, be it your hands, hair, or your laundry.

What does the hardness number on a water softener mean?

Water hardness is expressed in one of two units of measurement. The first unit is parts per million (ppm) of calcium carbonate, a term equivalent to the concentration of dissolved calcium and magnesium. Using this equivalent simplifies hardness calculations. One ppm means that one unit of calcium carbonate is dissolved in one million units of water. Parts per million is also equal to milligrams/liter (mg/l). The second expression of hardness is grains per gallon (gpg) of calcium carbonate.

https://www.aquatell.ca/pages/water-softener-selectorIf you have your water tested, the report will use one or both of these units to tell you how hard your water is. Since the level of calcium carbonate means little to water consumers, water specialists have classified levels of hardness. Most water hardness testers measure or report hard water in grains per gallon, but some laboratories use milligrams per liter or parts per million.

  • One grain per gallon (gpg) is equivalent to 17.14 parts per million (ppm). Water hardness can be measured in gpg or ppm, but gpg is the most commonly used measurement.
  • 20,000 – 80,000: This range signifies the grain capacity of most water softeners available on the market. Depending on your water hardness number, daily water use, and the number of people in the home, you may need a smaller—or larger—grain capacity softener. 

How to Test for Hard Water

If you have problems with soap scum or limescale, you may need to test for hard water. If you are a rural homeowner, you can purchase water hardness tests online. Type of hard water testers includes water hardness titration kits and easy-to-use test strips. Both tests for hard water use color changes to indicate the presence and severity of hard water. For urban homeowners, visit our water hardness level by city page to check your city's water quality.

Interpreting Water Hardness Testing Results

If your test of hard water results in measurements of less than 1 grain per gallon (17.1 milligrams per liter or less), you have soft water. Anything higher than this amount indicates hard water:

What is the Ideal Water Hardness?

Once you test your water and get your number, see where your water quality falls using the guide below:

  • 0–3: If your hard water test strip indicates that your water is between 0–3 grains per gallon, your water doesn’t require softening.
  • 3–7: Water between 3–7 gpg is moderately hard, causing spotty dishes and dry skin.
  • 7–11: Hard water is packed with minerals at 7–11 gpg, and you likely deal with crusty faucets and pipes and possibly reddish rings on your porcelain from excess iron.
  • 11–15: Considered very hard, water at 11–15 gpg exhibits all the signs of hard water all the time.
  • 15+: Extremely hard water is anything over 15 gpg.


Just because test results indicate hard water doesn’t mean you have to live with the damage water hardness causes. Water treatment technology such as water softeners are designed to treat water hardness, improving the water quality for your entire household. Interested in learning more? Check out Aquatell's water softeners today!