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Ask the Expert :: What is reserve capacity and why is it important?

By March 22, 2016 March 1st, 2021 No Comments


What is the “reserve capacity” for a water softener and why is it important? How do you calculate reserve?


A portion of your water softener’s total capacity is held aside as what is called “reserve.” Once you begin using those final gallons of soft water (ie. the “reserve capacity) your water softener will be triggered to regenerate at 2 a.m. Typically, your reserve capacity will be equal to one day’s worth of water usage so that if you begin using the soft water reserve early in the morning — during your shower at 6 a.m. for example — you will still have enough soft water to get you through the day before the softener cycles at 2 a.m. that night.

Calculating reserve as accurately as possible is important for minimizing the occurrence of hard water in the home and also for reducing the number of wasted soft water gallons. A reserve that is too high can result in soft water that is wasted. A reserve that is too low can result in occasional hard water.

A very basic way to calculate reserve is by using the industry figure of 75 gallons per person per day. This gives you a rough estimate of how much reserve you may need at a maximum.

A more accurate way to calculate reserve is by purchasing a water softener that can calculate your reserve for you based on your actual water usage. A few water softeners that are able to calculate reserve are the Fleck 6700 Upflow, Clack Millenium and the Fleck 5800 LXT. Soft water dealers estimate that these “variable reserve” features can save the home owner up to 30 percent on annual salt costs.

For an even more efficient system, you can choose a water softener with zero reserve. This means that you have no wasted gallons and you will never run into hard water. The Fleck 9100 SXT is a dual resin tank system that can go into immediate regeneration because you have two tanks for soft water. When one tank is depleted it immediately cycles and the water in your home begins flowing through the second tank. This is our most efficient residential water softening system and we would estimate an annual salt savings of at least 30-40 percent.

Want to know more about reserve capacity? Send an email to us at: sales@petersonsalt.com