We installed a new pump this year. I was advised to change from a 2hp pump to a 1.5hp. We have a 24ft AGP, with a 250 pound sand filter. I have had issues with my pump losing suction with anywhere from a .5 to 2 psi increase in pressure. I first noticed it when vacuuming and I was told there was an air leak. The pump filter basket has only a small air bubble that doesn't change size. I replaced the vacuum hose and the skimmer adapter - it still happens. I backwash it until clear and then for another 30 seconds to a minute - wasting a lot of water. When I turn it back on to filter it is 17psi. After vacuuming for anywhere from 30 seconds to 3 minutes, it loses suction and the psi may have gone up .5 to 2 psi. I then backwash and it doesn't even appear dirty. Everything I read says that you don't need to backwash until there is a 6-10 psi increase in filter pressure. Why would mine be .5-2psi increase? I replaced the pressure gauge yesterday. Is the 1.5hp pump undersized fro the 250 pound sand filter? I have been effectively fighting an algae bloom, but have the pool nearly clear.

Thanks for any advice.