Sizing a Water Softener Guide:

Sizing a Water Softer to a Home:

The first step to sizing a water softener to a home is to have the water tested for hardness levels which is measured in Grains (of minerals) per Gallon. If you do not live on city water you will also need your iron level tested. This is measured in Parts per Million. Once you have these numbers use the following formulas to find your hardness as well.

 

 

City Water:

  •   Number of people in your home x 75 x Grains Per Gallon Hardness.

  •   This would be your grains per day removal requirements. In this case 75 is the average number of gallons used

    per person per day.

  •   You can test for Grains per Gallon or your city water company may be able to give you an approximate GPG

Well Water:

 

  •   Find Compensated Hardness: (Parts per Million Iron x 4) + Grains per Gallon Hardness

  •   Number of people in your home x 75 x Compensated Hardness.

  •   This would be your grains per day removal requirements. In this case 75 is the average number of gallons used

    per person per day.

 

*For well water, any Iron levels of over 3 parts per million an iron filter may be needed depending on the size softener being used.

Example:

 

A family of 4 in Indianapolis needs to size a softener. Their grains per day needs are calculated below.

 

4 People X 75 gallons usage X 25 GPG hardness = 7500 Grains per Day 

Using Grains per Day to Select a Softener:

Now that we have the Grains Per Day it is easy to select a softener using the table below. Typically, is ideal for a softener to regenerate every 3 days. Softeners are sized in “cubes” or cubic feet of resin in the Mineral tank. In the table below the 3 Days for Regeneration column is the Grains per Day you wouldn’t want to get above.

In the example above, our Indianapolis family needs 7500 Grains per Day. In the 3 Days for Regeneration column we can see a 1 cube softener is 8000 grains per day and would work just fine.