Flexible metal duct to absorb rigid pipe expansion
In my house, I have standard metal ridged heating pipe and in some cases the run is long. When the furnace comes on the long pipe runs will make a banging noise or popping sound. I was talking to the people who installed the duct work and they said it was due to the expanding and contracting of the metal as it heats and cools and is normal. He said I could put in 6 inches of the flexible metal ducting in the middle of the run to absorb the movement which would eliminate the noise. The flexible duct I am talking about here is made of aluminum and is sold everywhere. Before I cut into all my long runs of ducting, has any one done this? Did it work?