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			#1  
			
			
			
			
			
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|   Is it a dual inline tds? They can be calibrated, but it comes calibrated from the factory and 3 months is not a long time.  Unless of course, it was bounced around during shipping. Maybe the LFS would check it where you bought it with their water. But even 1 ppm is not very much. Some people are using tap water without any trouble (not that I would recommend this though) If you have a dual tds, what is the tds of the incoming water? What is the tds of the exiting water from the membrane, before the DI? | 
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			#2  
			
			
			
			
			
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|   all depends on the post RO measurements to how hard the DI needs to work. TDS last time I measured in Edm was out of the tap at 168, 007 after my membrane and still get more than 6 months out of my DI resin. This is at about 2g a day plus water changes. 
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			#3  
			
			
			
			
			
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|   Its leaving my membrane at between 1 and 2 ppm.  Im starting to think maybe I got a bad DI replacement cartridge. . . Its a coralife R/o Unit |