Pressure rising quickly

[dsimpson]

To get the pressure back to 13psi I just unplug and leave off a bit and it will start over at 13 when I start back up. Pressure and flow are fine in recirculate mode. After backwashing same problem pressure rises from 13 to 20-23 in around 30 mins.

Thanks again

[Poconos]

Right now I don;t have any ideas other than the sand type that I mentioned above. Seems obvious it is a filter problem and one that takes time to occur. About the only thing that I can think of that matches that criteria would be fine sand eventually plugging the lateral slits.
Anyone with comments about grades and types of filter sand and this problem?
Al