I was thinking of setting up a dual di system (soft water area), i could test the water in (tap>tank) the water out the first di, then with another tds meter measure the water in and out of the other DI unit.
Im going from a post on Kev R's forum about dual DI set up, whereby using all the resin in DI cannister 1 until the TDS meets the tap water TDS, changing around the DI cannisters and fill up the one that runout with new resin, whereby fully utilizing all the resin.
I wanted to actually look how the meter was installed, in situ, and what fixings have been used.