Sm7400

Funny because as I typed that sentence I thought, wait a minute, that can't be right. So I went and unscrewed the the air relief on the filter and then the gauge and sure enough it didn't move. I still have a problem with sand getting into the pool after I do the rinse cycle. At first I thought it was because of the high pressure but it must be something else. When I do a backwash there is a valve on the pipe I need to open first. Should this be left open during the rinse cycle or closed? I'm not sure exactly where the water is going in the rinse cycle. If it's just going back into the pool then I will keep it closed obviously, but if its supposed to travel the same route as the backwash water I will keep it open. Thanks for the help.

The pool is about 20x40 ft, in ground and about 9 ft. deep. We recently replaced the liner and when the water all drained the concrete buckled in the deep and we had to do a lot of work. It ended up that we eliminated the bottom drain and were left over with the two skimmers. We're having a problem with the sand filter operating above 30+psi. I actually don't know what pressure it's operating at because the needle is pegged at the stop pin and the gauge only reads to 30PSI. I've done three backwashes in the last 24 hours and 3 rinse cycles. The sight glass runs clear after a few minutes each time. On the most recent backwash the hair filter in the pump filled with leaves so there was something clogged somewhere. After each time of doing the backwash/rinse the pool got sand in it and the pressure never dropped. Even when I turn the pump off the valve still sits at 20PSI (I don't know if this is normal, or if it takes a lot of time for the pressure to go down). Anyone have any thoughts? Filter is Jacuzzi Laser 225. Pump is 1HP.