I don't know much about DE filters but I do know that changing media won't fix a basic problem. I'm wondering, if in addition to SO's idea, if your pump is rated for a higher output than your filter's input, which is a common problem. A 1.5hp pump CAN be too strong, especially if it's a full-rated pump (most in ground pool pumps are). How big is your pool and what kind of pump is it?

You can go to Hayward-Pools.com and look up your owner's manual. It has several suggestions of possible causes of DE going back into your pool.