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 S4 flow rate=1.75seconds/ml +/- ~10% for me on my three tanks, but that was with +/- ~1' rise/drop depending on the tank.  I tested three of these on three tanks and ran various runs over several days with 12 daily doses of between 20 and 45 seconds/dose on a 100g/l Ca and a saturated dKh solution.  Remember after you change the setting you have to hit 'Save', I only mention because I forgot one time and was wondering the same.  Dan 
			
			
			
			
			
			
			
			
			
				
			
			
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