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					Originally Posted by  phi delt reefer
					 
				 
				I dont believe doser's can back siphon just given their design (liquid is pinched out in one direction) It's not a free flowing tube so its not like the return line in your tank. 
			
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 Some dosers will back-siphon because they use fewer rollers.  Dosers should have 4 rollers to prevent back-siphon.  Some only have 3.  Drew's Dosers and Profilux both use 4 rollers.