I have a Pentair/Hayward setup with sand filter. Thinking about adding a timer to my setup to run pump when needed. My question is when pump is turned off manually now, it loses its prime and when turned back on shoots dirty water back into pool. I guess when its losing prime its disturbing the sand bed??? I think from reading some of pool school it seems it is a pressure side leak? The strainer lid basket is tight. Could it be a gasket in the multiport valve itself?? When the pump is off, it seems you can hear water draining back into the filter almost as if the backwash setting is on and air can be felt coming out of the clear sight window. Any help would be greatly appreciated.