I am wondering why the returning water is so strong. I have two skimmers and a maindrain. I have to keep the three valves closed maybe a quarter otherwise I pull air. Nothing leaking on top. my pool is 16x32 x28. Starite S7D75 D.E. Filter with whisper flo 1.5 HP pump. PSI IS at 20 for start up. Do I need to re apply D.E.? It’s clean but every year the water comes out of the return harder than spa jets. Thanks