I have a Hayward GM series sand filter 1.2 effective filter area. I notice when I remove the clamp and pull the entire valve body off the tub, the "Main pipe" that goes down into the sand fits loosely onto the valve. I stirred up the sand and reassembled the filter. Upon starting the pump there was a brief discharge of sand. Is it possible that some water can be bypassing the sand and going between the pipe and valve body (where the pipe connects into the body). I noticed the pipe is abrased, where it connects into the valve body. Is there some dye or something I can place into the skimmer to test?