I have recently begun experiencing rushing water sounds when my heat turns on. I believe it is air in the system.
I have found what I believe to be the air bleeder valve for my upstairs zone. When I loosen the screw at the top of the valve, nothing happens. I have tried doing this with both the heat on and off.
I have about 12 PSI according to the gauge on the boiler. Is there something I am not doing right in order to purge the air from the system?
I have attached a few pictures of the valve. Do I need to loosen the top of the valve as well?