How To Determine What Size Water Softener Your Home Needs

8 June 2016
 Categories: Home & Garden, Blog


Hard water is a source of frustration for many people. It leaves spots on glassware, film in the shower, and clogs your pipes. Installing a water softener could solve all of your hard-water-related problems. But, when it comes to water softeners, size matters. Learn how to choose a water softener with a large enough grain capacity to handle your household's needs.

Look For Ferrous Iron

Water with ferrous iron appears clear when coming from the tap, but causes reddish-brown stains on things such as on toilet bowls, sinks, and dishes. If you think your water contains ferrous iron, you need to know your water's iron level before purchasing a water softener. So, test your water using a kit that measures water hardness and iron levels — not all test kits measure both.

Ferrous iron levels are measured in parts per million (ppm), and standard water softeners can typically remove ferrous iron if your iron level is lower than 4 ppm. However, if your iron level is 5 ppm or higher, you might need to purchase an iron filter in addition to your water softener to achieve the results you desire.

Test the Water Hardness

Water hardness is typically measured in grains per gallon (gpg). However, water hardness can also be measured in parts per million grains — one gpg equals 17.1 ppm. You should know both measurements just in case.

Most water hardness test kits measure grains per gallon. To convert grains per gallon to parts per million, multiply the number of grains per gallon by 17.1. (If you're looking at a parts per million measurement, you would divide the number by 17.1 to convert it to grains per gallon.)

Determine How Many Grains Need To Be Removed Daily

To determine the the amount of grain capacity your water softener needs to have, you need to calculate your average daily grain removal needs:

  1. Multiply the number of people in your household by 80 — the average amount of water one person uses daily in gallons. So, if you had four people living in your house, you'd multiply four by 80 to get 320.
  2. Multiply your result by the number of grains per gallon of water indicated on your water hardness test results. For example, if your family uses approximately 320 gallons of water daily and your water hardness is 10 gpg, you'd multiply 320 by 10 to get 3,200. If your water doesn't contain ferrous iron, the sum from this step is your water hardness value. If your water has ferrous iron, complete Step 3 to adjust the value.
  3. Add 3 gpg for every 1 ppm of iron to your total water hardness value. For example: if your water hardness value is 3,200 and your iron level is 4 ppm, you'd multiply three by four to get 12. Then, add 12 to 3,200 give you a total water hardness value of 3,212.

Determine the Proper Grain Capacity

The size of water softeners is measured by its grain capacity per regeneration cycle. Ideally, you want your water softener to regenerate approximately once per week. To determine your household's needs, multiply your water hardness value by seven. For example, if your water hardness value was 3,200, you'd multiply that by seven to get 22,400. So, you'd need to purchase a water softener with at least a 22,400 grain capacity for your home.

It takes a few minutes to calculate the amount of grain capacity your water softener needs, but it's a step you don't want to overlook. If you don't calculate the average grain capacity needed for your home, you may not purchase a water softener that can handle your family's needs. For more information, go to sites like