Weird Filter Issue

[tman777]

I've got an inground pool with a Hayward EC-65 DE filter using a 1hp superpump. I've had this system for four years and it has been running fine. This year something strange is happening.

At first the pump would not prime at all. I replaced every gasket and o-ring I could on the filter and the pump and that got me to where I am now. The system works fine IF I open the drain valve at the bottom of the filter. As soon as I do that the pump starts to pull water and will continue to after I close the drain (pretty hard to do with water jetting out). Of course this also dumps DE out of the filter so I keep having to add DE back in. I've been doing this in small amounts so as not to clog things up.

I thought this might be caused by blocked 'fingers' so I got some filter cleaner and soaked the filter for 24 hours and tried again. Pretty much the same thing continued to happen.

When the system is filtering it is sitting right around 10psi but if I try to vacuum the pressure drops to zero and the water flow eventually stops. I thought it might be a hole in my vacuum hose so I put a six foot length of hose in the skimmer instead and the same thing happened.

I've taken everything apart and reconnected it making sure every joint is sealed up with teflon tape and can't think of what else to try at this point. Any ideas?