I have a DE filter that looks more like a cartridge (Pentair ECDE60). Does anyone know how frequent the DE should be backwashed/filter grids cleaned? Everything I read says when the pressure gauge raises 10 PSI above normal, but my gauge is broken. My filter is so BASIC it doesn't have a backwash or waste setting. I just open the valve at the bottom of the filter once the pump is turned off, supply and return lines closed, and vent valve opened. Any help on how to backwash this type of filter configuration and/or for future spring pool openings will be greatly appreciated as I probably cleaned my filter 2 dozen times. Granted 18 of those were because I didn't balance my water before SLAMming, or so I figured.