We purchased our home six year's ago and we have a 55 year old furnace Thermo Pride and installed on it is a auto Flo model 200p power Humidifer. This Humidifer has never been used by us and is in the off position recently the Humidifer has started dripping water on the bsement floor from it's overflow tude if the unit is off why is this happening and how do I Stop it from leaking water out.