Have 72" Pentair DE filter. Replaced small grid which had holes. Cleaned all grids using dishwasher detergent. Reassembled and charged with 7 pounds of DE. Green pool. Pressure started at 15 but went to over 30 six hours later. Each time I backwashed and added small amount of DE the cycle time has decreased. 2 hours became 1 hour. Before backwashing when pressure was up to 35 I opened tank to look and see what shape filter was in and it had fairly thin algae film across all of grids but it wasn't really that built up. The metal "mushroom" on top of maninfold had 1/4" of stuff on it but the grids were more like a film. Just doesn't seem to be enough to explain the high pressure and the resulting slowdown of water flow. Pool is green but this short cycling is making it impossible to get any real water flow and I don't want to shock it until I'm in a position to really filter.
I've cleaned filter four times this summer (two times where I put it completely apart) and I'm thinking there is something else going on. Grids are around four years old and pool wasn't opened last two years. Wondering if grids have gone bad or if a full chemical clean would make a big difference. Any suggestions on what to do? I did notice that lines going into filter occassionally leak when I backwash.