:?: I'm really baffled on why my pump pressure jumps form 15 psi to 35? I first noticed this while trying to manually vaccum the pool. Pressure goes up, vaccum goes down! I've backwashed the filter, that solves the problem for about 10 minutes. Just long enough to make you mad!! Both clean out baskets are clean. I thought maybe the sand needed to be replaced, so I bought my pool filter sand at LOWES hardware. It did NOT solve the problem. I've replaced the main gasket on the multi-port valve and that it did NOT fix it either. I'm getting rather ticked off! After doing a backwash and just letting the pump run, the pressure stays down around 15-18 psi for about an hour than it will slowly make it's way to 35. I've looked for air at the pump clean out basket thinking it may be getting cavitated, but there is no air present. It's a 300 lb. sta-rite sand filter, sta-rite multi-port valve and a 1.5 hp pump. What could possibly be the problem?? Thank you