I'm still in the slamming stage and I have an air tight system. I can clearly see that there's no air in the sight glass of my pump. When I 1st turn on the the filter, I have GREAT pressure coming out of the jets and it slowly dies down after a couple of hours to hardly anything. I look back into the pump and there appears to be no air and plenty of water going in. I back washed and opened and removed the filter and cleaned it. I hosed the inside of the filter (DE filter by the way) and got my pressure back but only for a couple of hours again. Pressure in the gauge has gone up but the plastic valve knob seems a little worn and I'm replacing it tomorrow. I've read a lot about the pumping system in "pool school" but no real mention as to where I should go next with this " losing pressure". Is it just that I need to back wash more often? My pool has been neglected for 2 yrs by the previous home owners. HELLLLLPPPPP!!!!!