Hello,
So I have a pentair whisperflow, and a pentair cartridge filter on my inground pool. I have a check valve on the suction line and the pump seems to remain full of water overnight, keeping its prime. When the pump kicks on, i can turn the bleeder valve atop the filter and air will come out, and then eventually water. Once i shut the valve it stays that way, full of water. But overnight when the pump shuts off, the filter seems to lose the water in it and the next morning is half full of air again. Any idea whats going on?