Bent
I got nothin'
I've been using one of those Ultralife float switches for about 15 years now without any problems. I have it on a timer too, so instead of clicking on and off throughout the day, the tank is topped off once every 6 hours or so. This is probably the best piece of equipment I've ever bought to tell you the truth.
http://www.marinedepot.com/Ultralif...ug_In_Units-Ultralife-UL1111-FIDPETPU-vi.html
That's a good fail safe to do. Keeps the pump from running a hundred times a day.