Backwash

Backwashing cleans a sand or DE filter. Water runs backward through the media and out the waste line. It carries trapped dirt away.

Backwash when the pressure gauge rises well above the clean reading. Your filter's manual gives the exact rise. Run it until the sight glass clears, then rinse for as long as the filter manual says. Do not backwash too often, since the dirty layer helps filtering. Check local rules on where backwash water can go. A DE filter needs fresh powder after.