TOO MUCH BACKWASHING IS NOT A GOOD THING

How often do you backwash your filter?

We have come across many varied answers throughout our many Certified Pool/Spa Operator® (CPO®) Certification classes. Answers have been every day, once a week, once a month, when it needs it, to what is backwashing. Backwashing, in its simplest terms, is defined as the process of cleaning a swimming pool filter by reversing the flow of water through the filter. Only sand filters and diatomaceous earth (DE) filters can be backwashed.

For sand filters, manufactures recommend backwashing only when the filter pressure gets 8 - 10 psi above the last time you backwashed. On filters with both influent and effluent gauges, the differential should be 10-20 psi. As the filter starts to get dirty, the dirt clogs the pores in the sand and helps the filter to grab even smaller particles. Therefore, as the filter media becomes “dirtier” it is able to filter down to a smaller micron and work more efficiently.

For DE filters, backwashing is recommended the pressure reaches 10 psi over normal operating pressure. With DE filters in some areas, a separation tank is required to collect the backwashed water which include DE.  When a DE filter is backwashed, fresh DE needs to be added afterwards to recoat the screens.  For any filter, backwashing should be performed for 3-5 minutes or until the sight glass clears.

Excessive backwashing can be compared creating your own leak which is costly. Backwashing unnecessarily leads to increased costs for water, sewer, chemicals and time(labor). And if you're heating your pool, the cold water you put in lowers the water temp causing your heater to run more often which uses more energy.  This is why is it recommended to backwash based on pressure differentials and not a predetermined schedule of time.