Did you ever use DE powder to TEST your filter?

I'd like you to do that -- buy the smallest bag of DE you can find. Here's an example
http://www.lesliespool.com/Home/Filt...ies/14316.html

Add 2 cups of DE to your skimmer with the pump on, and then watch your returns. If you see DE shoot back into the pool as a white cloud, you need filter work.

If not, the DE will help you catch and clean up whatever your dust is. You can keep dosing with several cups of DE just before you vacuum, and it will help your filter trap any fine powder you vacuum up -- but it will also shorten intervals between filter cleaning.

Ben