Water can be used upto 015 before changing....if youve been told to change it when it goes over 000 then your resin supplier really knows how to make you line their pockets quicker
In my experience it can go from 0-50 in a matter of a couple of days so if you miss the crucial moment you will be cleaning windows with a very high tds.
I've check the tds coming out the ro (after the resin) 5 times since Thursday. It was 007, 009, 010, 007 and 006.Any ideas why it changes and would another resin cartridge get it down to zero? The resin being used is only about 2 weeks old.Cheers