I have a pressure relief valve on top of my furnace that will not stop leaking. I have replaced the exspansion tank because the bladder had went bad. I released some pressure from the new tank to 24.5 psi. I replaced the valve itself. I turned down the temp to 160 deg. I also checked the main pressure coming into the system and it is well below any level that would cause the valve to continue to leak. Still when my furnace kicks on to heat hot water the pressure builds to over 100 psi and the valve continues to leak.
Note, that this started to happen after splicing into hot and cold lines a couple weeks ago for a new bathroom. Any help would be great, Thanks!