What about a float switch from a pedestal style sump pump?I actually have one that isn't that old.The pump ingested something and we replaced the whole unit.You are welcome to it for the cost of shipping.The unit I have is quite similar to this one here http://www.contractorsdirect.com/General...t-Pump-VS-P2800 I think it would be fairly easy to mount the guide rod to the edge of the tank along with the switch.