I have a 15,000 gallon inground pool with main drain/skimmer/(2) returns, S180T filter and a Power Flo LX 1.5SPL pump. I have no problems getting it to Prime and I have zero issues when in recirc or sweeping to waste. I put the multiport valve into filter, runs for about 45 minutes then I see a loss of water through the pump strainer basket lid. I clear and debris from skimmer and I shut off the pump and then change to recirculation. Water level comes back up PSI goes back down to 10 and everything is moving well and then I move it to filter and it runs 45 minutes no problem and then back up to 15 psi and low water. Sometimes there isn't even anything in the skimmer to be cause any additional pressure loss. When I go to remove the pump cover there is quite a bit of pressure and is hard to remove.