Did you flush the RO
membrane for a couple of hours before hooking up the DI
cartridge? The RO
membrane is packed in some chemicals that will wipe out a DI
cart in short order. I flushed mine for a while and my first DI
was still gone after about 75 gal
of production. I changed it and this one has made several hundred gallons with little color change...TDS
is still at 1.
Also, do you know what your water pressure is? Mine runs from 40-60lbs depending on the mood of the well pump. Low pressure will cause high TDS
from the membrane which will also deplete the DI
cart quickly. I don't remember what my TDS
out of the membrane was...about 14 I think. It is 77 going in from the water line.