I wonder if your valve has a 'Rinse' position and if you have a sand filter? Typically after backwashing, you go to rinse for only 10 seconds or so to blow anything out the waste instead of into the pool. Rinse puts the filter in the normal filter flow mode but directs the output to waste. To catch really fine stuff with a sand filter you may want to consider adding a little DE powder. Check post-2 of this thread:
http://www.poolforum.com/pf2/showthr...ht=%28ajs-1%29
Al