The Importance of Backwash Rate

by Scott Harmon


All filters clean in backwash. In order to achieve a proper bed expansion for cleaning, choosing your media is, in many cases, dependent on the well pump flow rate. There is no cheating here.

If the chosen filter requires a backwash flow rate of 10 gpm and the pump only produces 7 gpm, the bed will not clean completely and though it may take a few months to a year, the bed will foul prematurely.

Water temperature also plays a role in selecting the right equipment. Colder water will expand the mineral bed more than warmer water at the same flow rate.

For example, when comparing water at 40 degrees Fahrenheit with water at 80 degrees Fahrenheit, the mineral bed will expand approximately twice as much at the same flow rate.

If the manufacturer of the mineral you are using recommends backwash rate of 10 to 12 gpm per square foot, use the low range on cold water and the high range on warmer water.


Scott Harmon CWS V, CI is manager of technical support for the RainSoft division of Aquion Partners L.P, Elk Grove Village, IL. Harmon started in the water treatment industry as an installer and service technician, and was the service manager for a local RainSoft dealer before joining Aquion as international service trainer.

By the same author on our site:

Identifying Types of Iron

The Basics of Iron Removal

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