I have a 16 x 40 pool with a saltwater generator I have a Nautilus F.N.S. 60 filter I believe it is made by pac fab My problem is that I have de powder coming back into the pool I have manually and chemically cleaned the grids I do not see any holes or tears I have replaced all the o-rings that I can find, have replaced the spider gasket in the multi-port valve and I am almost 100% sure that it is not coming from there. Can anyone tell me what other problems could be causing the de powder to go back into the pool please help dont know wher to go next