No need to test for that stuff with a ro
unit, it will remove it all.
= total dissolved solids, on a new unit it should be 0. As the resin in the di
wears out it will rise. If you can get a DI
cartridge to last a year as they advertise that would be a miracle. I'm lucks if I get a few months out of my dual DI
system. It will all depend on the water quality you start with. Test your water from the tap with the TDS
and then the end product and you will see the difference.