I have one from autotopoff.com and a DIY. Basically just a float switch with a DC relay and AC/DC converter (cell phone charger plug, etc.). I've had some issues out of the DIY, but only when I let the top off reservoir run dry (the switch gets tricked if it isn't allow to turn everything on and off when it wants for some reason). Never had any issues out of the ato.com part, though (working on five years years).