When we moved into our house, we were delighted to find a section of pipes vibrated extremely loudly, while toilet was filling or sink was running. I replaced the toilet, but the vibration remained. Then, I drained the entire system...hot and cold lines, including the water tank. Filled it all back up, purged air out of the lines, and vibration was gone. I don't have much explanation, but it worked. Could've been bad angle stop valves, they were shot after 20 years, but I didn't touch them at the time.
Thanks, have done that with no effect.
digitalplumber is just a name for use here, I am not a plumber!