Last year I ran my filter 24/7 for weeks at a time without the pressure going up at all. I would always get worried, add some DE to the sand filter, and within 8-12 hours, the pressure would be up by 10-15 psi. Is there something that would be causing the filter to not work correctly?
I did all the trouble shooting stuff last year by looking at the laterals and checking the sand. The sand was perfect. I even took it to the pool store. They said it looked just fine. The laterals were all in perfect working condition as well.