I am new to having a sand filter. Is it normal to have to backwash after every vacuum. The pool has only been up 2 days and both days I vacuumed and both times I had to backwash. After vacuuming the filter strainer on the pump was full of water. Usually when I run the filter there is no water in there. I turned the pump back on after vacuuming and the water was still there and it didn't look right so I backwashed and it did go away. The following day same thing. Is this normal or am I doing something wrong?