Softener Sizing

To size a water softener for your customer, you must know three things:

  1. Hardness in GPG
  2. Iron in PPM
  3. Daily usage

1. With the hardness and iron content, we will determine the COMPENSATED HARDNESS

(If the hardness is provided in ppm, convert it to GPG by dividing the ppm by 17.1)

To determine the COMPENSATED HARDNESS we use a conversion factor as follows...

(Hardness GPG X 1) + (Iron ppm X 4) = COMPENSATED HARDNESS GPG

This provides us with compensated hardness.

Note: most softeners are only rated to remove up to 2ppm iron and additional treatment may be necessary for higher levels of iron.

2. We must determine daily usage. A simple method is to take the number of people in the home and multiply by 75 gallons per day per person.

3. The last factor to consider is the number of days between regenerations. Typically, this is between 3 and 5 days.

Now we will multiply our compensated hardness by our gallons per day and multiply the result by days between regenerations to achieve our suggested water softener size in grains.

For Example:

      • Hardness = 20 gpg   —   20 gpg X 1 = 20
      • Iron = 2 ppm   —   2 ppm X 4 = 8
      • Compensated Hardness   —   8 + 20 = 28 gpg
      • Water Usage = 300 gpd
      • Days between regenerations = 3
      • 28 gpg X 300 gpd X 3 days = 25,200 grains required

Round UP to the closest size softener available. In this case, we could choose a 9” X 48” at 15lb salt dosing or a 10” X 44” with 9lb salt dosing.