How to determine water softener size

Written by j. johnson
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Water softening is a technique that removes calcium, magnesium and sometimes iron from water, turning it from hard water to soft water. When your water is hard, you run the risk of having clogged pipes, and soaps and detergents may not be able to properly dissolve in the water. A water softener unit will remove these potentially harmful minerals.

Skill level:
Moderately Easy

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  1. 1

    Figure out how much water your household uses in an average day. Take the number of people in your household and multiply that number by 75 gallons, or the average amount of water used by most people in a day. If you feel your household may be different from the average, use the Water Use Calculator in the Resources section to calculate this number.

  2. 2

    Multiply the amount of water used in your household each day by 10 GPG. The number 10 is the most common GPG, or grains per gallon. You can also look at the United States Water Hardness Map in the Resources. The number you get after multiplying the amount of water used per day by the GPG is the grains per day for your household.

  3. 3

    Use the number of grains per day you found for your household to find the corresponding number on the Water Use Calculator. This is the amount of grain capacity you need your water softener to have. For example, if you calculated 3,000 grains per day, you need a water softener that has a 24,000-grain capacity.

Tips and warnings

  • You can also contact your city water department to find the GPG for your water.

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