A pool filter needs to be backwashed whenever its pressure gauge rises to a point 8 to 10 pounds above the starting pressure it shows when the filter is clean. The pressure gauge needs to be checked weekly.
The backwash process cleans the pool filtering unit. Rising pressure in the filter indicates that it takes more force to push water through the unit because of accumulated dirt and debris. When the pressure has risen at least 8 pounds, it is time to complete the backwash process, which varies depending on the type of filter. Backwashing too often wears filters out early and wastes water. On the other hand, backwashing too infrequently leads to clogged filters and a dirty pool.