I have an above ground pool that has low pressure. At first my PSI was showing 50 so I changed the reader. Now its showing 9 PSI. Its pumping ok but not enough to go back into the intake. I cannot use my vacuum and hose do to low pressure. zi think it should be at 15 psi. I cleaned the skimmer, skimmer at pump, backwash, rinsed and check for leaks. Is there something I'm missing? I recently changed the hoses to the pump. How long should the hose be to the pump? Is there something else I can do for the sand filter?