David,
You need an ASV (auto shut off valve) and a float switch (something like you see on your toilet tank). You can get it as a kit.
Are you still interested in getting the RO setup I have? Email me.
vlam168@gmail.com
BTW: this is an example of a kit that you would need.
http://www.drsfostersmith.com/produc...m?pcatid=14690