I have a Pentair FNS Plus 60 DE filter on my pool. I disassembled the grids today to do a manual clean/soak on the grids. Six of the eight grid frames were broke near the top of the return pipe. It has been one year since the filter was last manually cleaned. The last time it was cleaned I had to replace 4 broken/torn grids. None of the filter grids' cloth was torn this time. I normally have not done this maintenance, a pool proffessional has been doing it for me. After what I found today, maybe I should be doing this job myself. The bttom half of the filter house was about 30% filled with D.E. and the grids were packed with DE muck between the grids. I now know, from reading here on the forum, that I have been overcharging my filter w/ DE after a backwash. I should have been using only 5 scoops rather than the 6 required after a manual cleaning. But why are the frames breaking on my grids? I normally backwash after I see a about 5 psi delta from the initial pressure after backwashing. Is it normal for the grid frames to break like this? I assume it is necessary to replace the grids when you find a broken frame or is it? Do most of you manually clean your DE filters more frequently? Looking for your advice and experience.
Thanks in Advance!
note; the grids are Unicel replacements.