HVAC Questions? Ask an HVAC Expert for Answers ASAP
Sorry at work currently.
We need to find where the vibration is coming from to start with. No rush, let's just wait until it makes the noise again and then feel every valve.
OK, so the pressure relief valve or temperature/pressure relief valve both discharge into the same pipe. These valves do not last forever and may be a simple swap.
Try and see which one is dripping next time you get the noise.
Just come back when you see one dripping.