Lenny, if I really want to do a good backwashing - I'll do backwash/rinse 3- 6 times then add a ~1 min filter cycle and backwash/rinse again. Getting the water running the oposite way seems to loosen up more of the DE so you can get a little more of it out. (to prevent any 'back-talk' -- I rarely backwash filters, it's just easier to break them down and hose them off, and this way I can see if the homeowner has been under or overcharging the filter )