Hi there, new to owning a DE filter but learning as I go. The filter itself is a Spartan (company no longer exists) with Hayward controls so it's an old one. Problem is, when it's run for a couple hours it starts acting like it needs to be backwashed ie: low return pressure, sounds like it's trying to refill the tank etc. but when I shut it off it will belch out the return jet and send a 5-6ft tall geiser out the skimmer, it seems to empty the whole filter tank as I have to then wait for it to refill before it will backwash and rinse. The pressure prior to shutting it off is between 20 and 25psi. I have a 10,000 gallon above ground pool, so it has about 3 lbs. of fresh DE in it and a new seal around the tank. Now if I go right back out within an hour or so and shut it off to backwash and rinse again I don't get the geiser just a small belch out of the skimmer. A few weeks ago it ran fairly normal at 15-20psi and only did this when I knew the DE was low--but right now there is plenty of DE in it and it's still doing this. Any advice will be greatly appreciated. Thanks!