brooklyn ny
New Member
I have a flue pipe running through a chase in the corner of my bedroom that makes knocking noises every time the boiler turns on, loud enough to wake us at night. This is in a three story row house. There is a gas boiler (175k BTU) for heat, and two water heater tanks, located in the cellar — all three are connected to the same exhaust flue pipe, which runs straight up to the roof through all three stories above. I believe the flue pipe is 8-inch B-vent galvanized steel. The heating system is hot water radiators. Whenever the heat is turned on, the knocking in the flue starts, most loudly on the top floors closest to the roof (and unfortunately where my bedroom is located).
I suspect the noise is due to thermal expansion in the flue pipe. I opened a hole in the drywall in my bedroom and saw that there was a tight fit between the flue pipe and the floorboards. I sawed away the floor enough to leave a slight gap (see attached photo), thinking it would give the pipe more room to expand, but this didn’t alleviate the noise.
Any ideas on how to address this? Perhaps the cold air from the roof meeting the hot exhaust will cause noisy thermal expansion no matter how tightly or loosely the flue pipe is held in place?
Thank you in advance for any input.
I suspect the noise is due to thermal expansion in the flue pipe. I opened a hole in the drywall in my bedroom and saw that there was a tight fit between the flue pipe and the floorboards. I sawed away the floor enough to leave a slight gap (see attached photo), thinking it would give the pipe more room to expand, but this didn’t alleviate the noise.
Any ideas on how to address this? Perhaps the cold air from the roof meeting the hot exhaust will cause noisy thermal expansion no matter how tightly or loosely the flue pipe is held in place?
