How To Size A Water Softener

When it comes to buying new water softer, it’s important to select a unit that is of the right size or capacity. Generally, you want to go with a unit that can handle the daily water demands of your household.

Picking an undersized system in a home that requires high flow rates or capacity will disappoint you as it will not provide sufficient contact time for the softener to work effectively.

On the other hand, using an oversized system in a household with low demand will lead to a waste of materials and money.

Usually, the capacity of water softeners is expressed in grains per minute which reflects the number of grains of hardness in the water they can handle between regeneration cycles. The higher the grain ratings, the higher the capacity.

Ideally, you need to consider your household’s daily water usage as well as the time length between regenerations to determine the ideal size or capacity of the water softener you should get.

One recommended formula that can help you easily calculate the right size of water softener your household needs is multiplying the number of people living in your home by the amount of water they use each day which is usually 75 gallons (the average number of gallons that one person can use per day).

Once you have the total amount of water the entire household uses daily, the next thing is to multiply it by the hardness level (grains per gallon) of your water and days between regenerations to get the approximate capacity of the water softener you need.

So, Capacity = (Number of People + 1 for appliances) x 75 Gallons x Hardness Level x Days between Regenerations.

For example, if your family has 5 members, your water hardness level is 10 GPG, and you want a unit with a 7-day regeneration cycle, then the minimum water softener capacity you will need should be

 (5+1) x 75 x 10 x 7 = 31, 500 grains.

The actual amount of water used by one person per day may vary though, so you may adjust the number accordingly to better reflect the average daily usage of your family members.

It’s also recommended to add 1 to the total number of people in the house to cover the appliances so that you can pick a unit with sufficient capacity to supply your entire house and meet the needs of everybody.

Moreover, you don’t want a system that does very frequent regenerations because the backwash process involves wasting some water based on the size of your softener plus the regeneration cycles can take between 1 to 2 hours at a time, and during this period no softened water is produced.

Besides this, it’s not advisable to select a water softener that goes more than two weeks before regenerating, even if it’s a high-grain system. Waiting too long can certainly lead to the compacting of resin and the emergence of foul smell resulting from the minerals, especially iron. 

Therefore, the ideal unit is one that takes at least three days before the next regeneration cycle and won’t go more than a fortnight without regenerating.