You can install your RO filter anywhere that the drain line coming from the unit is above a drain, some people even run the drain to a large container such as a large (32-50 Gallon) trash can and then use the collected drain-water for other uses. RO's use a lot more water than they produce, mainly depending on water pressure and water temperature. You do have to worry about overflowing the container though. Most people just drain to a waste drain, floor or drain trap under sink. Most RO's come with an adapter where you pull water from your cold water supply valve that feeds your faucet. If you need to place your unit in a cabinet above your sink you can cheaply get more tubing and Johnny Quest type fittings at places like Home Dept or Lowe's. Net sites like freshwatersystems.com, or waterfiltersonline.com, have lots of laymen directions for RO installation to include pressure shut off systems. By the way you do not need to use the tank if you are just going to produce water for your tank(s). A small RO has a flow rate which is basically a trickle so the tank is so you can easily draw off 6-8 cups of water quickly for coffee or cooking etc. All kinds of shutoffs, float switches, and pressure increasing pumps are sold for custom or problem systems. Blah sa, blah sa, blah. long winded again.