hot water furnace?
Answers:
Well its a bit of a waste of water.......I would just turn off the power or gas, and also turn off the water supply to the unit, and just take the pressure off by opening a tap.
Other answers:
Drain it. Make certain the power to it is disconected!
Drain it. Make certain the power to it is disconected!
its up 2 u...
If it is a "Sealed System" there should be a rust inhibitor mixed into the water, in that case turn off the power and leave it. If not turn off the water supply, and the power and leave the water in the system. The oxygen in the air and the moisture you can't remove will speed up the corrosion process.