Here is an inexpensive float valve,
http://www.marinedepot.com/md_viewIt...product=KM1675
I used a pump and switch and had a flood when the switch stuck on. Two
switches would have worked better one cut on and one emergency
cut off. For now I just turn the pump on and off manually to top off
which is still better than dipping water out of a bucket. When I get
time I will rig a float valve to my RO/DI unit. Good luck.

Dinky wrote:
I have found a couple auto-top-off plans on the net, but they are
either so poorly written that I cannot follow them, or include the
use of expensive pumps, switches, sensors, and valves. I'm not in a
position to spend much money at this point, but with the switch to a
refugium\sump from my bigass sump I took out has resulted in the need
for such a device.
I'm looking for a very basic system, gravity\siphon-fed. I can
build\fabricate most components myself, and have tubing, acrylic and
many other materials on hand.

tia


--
John N. Gretchen III
Port O'Connor TX
http://www.tisd.net/~jng3