First, Thanks for taking time to look at my question.
Alright, heres the situation. I have a 16 two bedroom apartment building using a central boiler to heat the apartments. The tubing ran through out is the old gray Polybuetelene (PB) connecting to baseboard radiators (alum. finned copper pipes). On the top floor of an end apartment I am hearing a pipe or something "vibrating" "rattling" inside the wall. The best way that ive found to describe it is like a cabinet door closing and boucing against the frame of the cabinet. I only hear it about every 5 or so min. Its very random on loudness and when it happens. I tried bleeding air out of the line from a small bleader port but just got water. Im stumpped and so is my parts house. Any suggestions. Thanks again for your help.
P>S> If anymore info is needed please let me know.