You risk siphoning your tank if you fully submerge. I think the instructions also state to not do this. Since my doser is under the floor I can't press the button to see if it can pump past the blockage/skinned over end of the tube so I just clean it out quick. I imagine it still pushes past it but I'd rather be safe. 
		
	
		
		
		
		
			
		
		
		
		
	
		
		
	
	
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