Just noticed a brown stain on my dinning room ceiling. It's almost directly above a cast iron radiator on the second floor. I know the water in the system gets iron deposits which must be why it's brown. The heating system was running when I noticed the stain and checked the upstairs radiator. The ceiling and radiator were bone dry. I'm guessing the leak is at the union. Any idea on what the least invasive way to figure this out is?
I would guess I need to take the value off then the pipe connected to the elbow. If I'm lucky the problem will be there, right? If the problem is on the other side of the union, what then? Thank you, greatly.