I don't care how brilliant the design I would never attach a RO/DI unit directly to a top off.  I have a 100GPD RO/DI and would not want a failure in that to flood my system. 
 
Having a holding tank that supplies your AUTO-TOP-OFF is still and AUTO-TOP-OFF. 
 
 
J 
		
	
		
		
		
		
			
		
		
		
		
	
		
		
	
	
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