Can the grids go bad on a 4 year old Pentair DE filter? They do not clean up during a normal BW,rinse,BW,rinse,BW,rinse cycle. If I take the filter apart after the BW rinse cycles the grids are still caked with debris. If I remove the grids, hose them off, reinstall them in order and reassemble the filter housing the R pressure comes down to 18psi. I have plenty of pump pressure, the valve appears to be switching fine. The pool stays clean, but again I cannot seem to get the grids clean during BW.
Its a salt water, 40K gallon pool and I have just recently had this problom. Yesterday I was looking at 30psi of R pressure so I BW for 3 mins, rinsed for 90 seconds and repeated 3 times but I never saw any dirty disscharge through the transparent waste water tube. The disscharge flow out of the waste water pipe was great but like I said the waste water was clear as a bell. the R pressure droped to 20PSI but I have yet to add any DE. I usually add about 8 cups of DE after BW.I just checked and I am approaching 30PSI of R pressure again. I bet if I pull the filter apart I will find stopped up grids! Again, pool water stays crystal clear. The mainfolds in the filter look OK. Any ideas