The biggest difference I see with some of the units on Ebay is that they have a smaller
DI chamber than say a Kent or Captive Purity unit. I'm using one of the "generic" units here with the smaller
DI filter and it works great. It uses the Dow
RO membrane which is something you want to look for when you buy a unit. Mine is a 100 GPD
RO/
DI with a 5 micron sediment, 1 micron sediment, carbon block,
RO, and then
DI.
TDS going in is 162.
TDS out of the membrane is 13.
TDS out of the
DI varies between 1 and 0 depending on the mood of my
TDS meter. The small
DI carts are refillable if you want to bother with it. I don't know that it would really save that much money as I haven't checked on the price of the resin yet.
JMHO.