My house has baseboard heating from a natural gas water boiler and I am hearing some rattling when I turn on the heat at night on the 2nd floor. My house has 2 zones and I believe the issue is that air is trapped upstairs in the baseboard.
I inspected all the baseboard units and found that there is no bleeder value anywhere.
I also tried draining air from the boiler (which is in the basement) and that didn't help. Each zone has a drain but it is located in the basement. I did open each zone in a bucket of water and small bubbles came out but that didn't help.
Also I noticed that there is an upside down U of piping hidden behind a false baseboard in a small closet - I am not sure of its purpose - there are no valves there - just pipe and elbows.
- Should I installed a T or bleeder value to remove the air on the 2nd floor?
- What is the purpose of the upside down U plumbing?
- Beside air, could anything else be causing the noise?