k residential slantfin boiler with leaking relief valve, pressure builds to 30 and valve pops? steady stream of water leaking from pressure valve. put new watts feed valve and new expansion tank with new air bleed valve too??? still hitn 30 psi and popn the relief valve? boiler has five zones and one of those zones is domestic water. help?

 

Please clarify this a bit... do you have an 'indirect' water heater storage tank? Or a coil in the boiler itself?

Before you installed the new expansion tank, did you verify that the air charge was at 12 PSI?

After you replace the parts that you replaced, and turned the water back on, did the pressure come up to 12 PSI and stabilize there, and then only shoot up after it was heated?

OR,

Even without running the boiler, did the pressure rise up all on it's own, without heat from the fire?

Presuming that the new parts were installed and adjusted properly, the only other reason for this to happen would be either a leak in the tankless coil (if installed), or a leak in the heat exchanger in the indirect water heater tank.

 

Yes its an indirect water tank and I'm sure it has and internal heat exchanger. I didn't verify the charge on the expansion tank however it did state that they are shipped with a 12 psi charge as the new feed valve is set to 12-15 psi as well. after putting new parts on turned water back on and before i fired it the pressure read at about 10 or so but once i fired it, it slowly climbed to 30 and of course the pressure valve pops and so on. after some research on the indirect water tank I've learned its 8-9 years old and has never been maintanced??

 

its the indirect water heater, I isolated it from the system and boiler maintained about 12 psi so the heat exchanger is shot. its a 65 gal bradford white. does anybody have an idea how much these things cost?