Hello this is my first posting. I have a Hayward sand filter s244t my clean operating pressure is 35psi. The Hayward people say that is high for a normal running filter. They say I should check the sand and the laterals.Why would the pressure be high if the sand was old or there was something wrong with the sand or laterals? I'm not trying to argue just trying to understand what is going on inside the filter and how they work. Also the filter is plumbed with 1 1/2 pvc schd. 40 but at the fitting I don't see the usual purple cleaner stains that result from the glue up. Instead I see a white opaque residue. If I replace the sand I'll have to cut the pvc and install unions. I was wondering if there is some special glue. One more thing is there a place on-line or literiture I can get that can walk me through these repairs instead of diving in blind. We live in the southern Monmouth County region of N.J.. Thanks