Without tanks have two styles. Those with auto shutoff valves (look like below link), they shutoff when there is a a blockage of permeate water (good stuff) so you don't continue running waste water down the drain, that is what the float valve on mine does. Then there are those without an auto shutoff valve that will just continue to waste water through the waiste water drain.

http://www.airwaterice.com/product/PR-CV0201W