We've had our pool for a year now (yea!). For that entire time, the water has been crystal clear -- except the first month of pool ownership when I listened to a pool store tell me to lower my phosphates, and the stuff I poured in clouded my water (that was just before I found this forum!).

During that time, our DE filter has been flushed about six times or so (the first three times were within the first month of ownership, then a fourth time last August, a fifth time this past January, and I just flushed it for the sixth time today). The pool builder's pool start-up guy said that the DE filter should be disassembled and given a thorough cleaning at least once a year. I'm not willing to do that myself, so I'll pay a pool maintenance guy to do that for me.

Question: This forum is all about flaunting "conventional wisdom" and using tried-in-the-field practices for maintaining one's pool. What is the collective wisdom for knowing when you're really supposed to disassemble one's DE filter and manually clean the grids (either with a garden hose and/or soaking them in muriatic acid)?

Last August, when I backwashed the DE filter, the just-flushed, "clean" water pressure was 12lbs (with variable speed pump running @ 2750rpms). Then in January, I was surprised that the "clean" pressure was a little lower, just over 10lbs (same pump speed, same valve settings). Today, after backwashing, the clean water pressure is again 10lbs. So, I'm guessing that there isn't much old DE stuck to the filter grids, because each time I flush, I'm adding another 6lbs of DE powder through the skimmer.

Thoughts?