The pressure relief valve on the hydronic system boiler is releasing a little water every time the boiler cycle is almost done and I looked at the gage and its rising to about 30 psi, But I can't figure why the temp is always rising. I already changed the expension tank and TPR so whats now?

  • What is your normal boiler pressure? When you changed the expansion tank, what did you set the pre-fill pressure to?
    – Ecnerwal
    Commented Jun 2, 2016 at 16:31
  • @ Ecnerwal normal pressure is about 15 psi. the tank comes pre-filled to 12 psi
    – aofkj
    Commented Jun 6, 2016 at 14:47

1 Answer 1


Do you have an automatic fill valve? Is there a manual valve in line with it? Try closing the manual valve if there is one. If that solves your problem, adjust and/or replace the automatic fill valve.

If you have a (domestic/potable) hot water coil, that could be leaking into the boiler, too. Shut off the domestic hot water supply on the cold side of the boiler to diagnose that possibility.

  • I just changed the pressure regulator to a new one (15 psi) and the problem persists
    – aofkj
    Commented Jun 6, 2016 at 14:44
  • Have you tried shutting OFF the supply to the system (which I suggested doing before you wandered off into replacing parts that might not be broken?) And the supply to a domestic hot water coil, if any (or simply shutoff the main water supply valve for a while which should cover both of those, and then work backwards from what that indicates.)
    – Ecnerwal
    Commented Jun 6, 2016 at 19:37
  • Yes I did shut off the water and the pressure did not rise and no dripping.
    – aofkj
    Commented Jun 6, 2016 at 20:50
  • No hot water coil
    – aofkj
    Commented Jun 6, 2016 at 20:51

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