A thin mesh net catches the dirt. but it is immediately sent back into the nearby incoming water stream by a thin stream of water.
Once the main liquid stream is finished, or periodically for a continuous stream, the highly concentrated dirty liquid which is just ahead of the net can be directed or rinsed out to storage or to removal pipes.-- pashute, Jul 24 2011 Sand filter backwash cleaning http://www.viddler....ore/Glynn/videos/7/ [mouseposture, Jul 24 2011] Try this http://www.amiad.es...ater_Filtration.pdfor Google 'autostrainer principles' [Ling, Jul 27 2011] This is so close to a candle type auto-strainer, that it would probably be best for you to check one out and see if it matches your idea.-- Ling, Jul 24 2011 but mine is not once in while backwash, but rather continued backwash, where the dirt almost never reaches the net (or sand) in the first place.
ling could you give a link?-- pashute, Jul 27 2011 How can the dirt never reach the filter ?-- FlyingToaster, Jul 27 2011 random, halfbakery