R/O Units

[tyrfing]

In this forum I've talked with several people about R/O units and I am now convinced that I need to buy one. Since I am starting another 125 gallon tank, tne unit will pay for itself just in H20 from the market.
Question:
Can I hang a R/O unit on one of my chemical drums I am currently storing water in? My goal is to transfer tap into one of the barrels and let the unit do the work. Do I constantly need to be hooked to a water source? I guess my questions are pretty basic but I would like to learn as much as possible before I purchase.

 

[jtoliver]

You have to hook it up to your water pipes and then the water goes out of it into your storage tank. I have mine mounted on the wall in the basement and it then goes directly into a float valve in my sump and I don't have to worry about top offs.