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What Size Water Softener Do I Need?

It is easy to determine what size water softener you need once you understand how a water softener works. And, the good news is that there are several sizes of water softeners that handle small, medium, and large size requirements. You can determine what size is right for you by just following a simple formula.

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Understanding How a Water Softener Works

When there are large amounts of calcium or magnesium in your tap water your water is considered "hard" water. There are several signs of hard water. One very obvious and annoying sign is that when calcium or magnesium are present in your water your soap does not lather very well when you are trying to bathe. Other signs will be scale build up in toilet bowls, on the inside of your water pipes and water heaters, and even scale build up on the inside of your tea kettle.

The use of a water softener alleviates these problems. A water softener works by replacing the calcium and magnesium ions that are in your water with sodium or potassium ions. It is a simple process where the water in your home is cycled through a resin bed. A resin bed is made up of resin beads that have bonded with sodium ions. When the water in your home is cycled through the water softener or resin bed the sodium ions swap with the calcium and magnesium ions - thus taking the hardness out of the water.

Note: Eventually the resin bed will need to regenerate due to the presence of only calcium and magnesium, due to the exchange of ions that takes place during the water softening process. This regeneration process is done by the timers on the unit or by DIR controls (demand-initiated regeneration) which sense when the unit should recharge or regenerate.


Now that you know how a water softener works you need to determine what size water softener you will need. Water softeners come in many sizes. The size is determined by the amount of grains of hardness that a unit can cycle before it needs to regenerate. Water softeners should only need to regenerate every three days and ideally every seven days.

Small units handle from 12,000-16,000 grains, medium units handle from 20,000-40,000 grains, and large units are above 40,000 grains. The average number of gallons of water that a person uses every day is determined to be 75 gallons of water. Multiply the number of persons in your home by 75 to determine the number of gallons of water that you are using per day. You will need to know the GPG or gallons per grain (hardness) of your water. In most areas the GPG is 20 but to be certain purchase a water hardness test kit. Next multiply the total number of gallons of water used per day times the GPG.

For example a household of 5 people times 75 equals 375 gallons of water a day times 20 equals 7,500 GPG per day. And, since the water softener should recycle or regenerate every 3 days (3 times 7,500 equals 22,500) a medium sized unit should suffice.


There are several things that a homeowner should be aware of when it comes to maintaining a water softener. The resin bed is flushed by a brine solution that has been mixed in the water softener's brine tank. After the resin bed is flushed the used brine solution is flushed into a drainpipe. You may have to at times flush the brine line or clean the injector of your water softener. Since not all water softeners are the same, refer to the owner's manual for the correct procedure.

You will need to add salt to the water softener when the water level in the brine tank becomes higher than the salt level in the brine tank.

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About the Author

Paula M. Ezop’s inspirational column "Following the Spiritual Soul" appeared in "Oconee Today," a Scripps Howard publication. She has published her first book, "SPIRITUALITY for Mommies," and her children's chapter book, "The Adventures of Penelope Star," will be published by Wiggles Press. Ezop has a Bachelor of Arts degree from Northeastern Illinois University and has been writing for 10 years.

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