My RODI system has a pressure tank and I run about 40' of 1/4" tubing to get to my fish room. There I have a float valve in my sump and also in my RODI storage tank. I have run this type of ATO since 1998 without problems. Dump the fancy ATO's and go with the simplistic approach. Finally, Todd says you need the reservoir above the tank, but that isn't necessarily so. Another reefer uses an aqualifter pump rated at 3.5 gal per hour to move his water from the reservoir to the float valve. Works very well and cost about $12.00.