Buying RO / DI - I know nothing

[hillegom]

I see that link to costco has a pic of the unit. This is a new system and I have not seen one yet. I guess it doesn't waste water as it uses the pump, electrically operated, to push all the water through the RO membrane. But this would coat the membrane with all the "bad" molecules you would normally pass out to the drain. So I would check to see how long of a life the membrane is rated for.
Normaly, Ro units make one gallon of good water and 4 gal down the drain. This will flush all the bad things down the drain, and this will lengthen the life of the RO membrane .
You could always plumb the drain water outside and water the lawn. Good only in the summer though!