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Gnarly Leaking Valve on Hydronic Baseboard

Hi All,

So I'm new to hydronic systems -- we've had steam and forced air in the past -- but we just bought a house with hydronic baseboard heat. One of the most immediate things I've noticed is that, although our boiler is new, all the baseboards have really old valves.

This gnarly one was recently leaking/dripping when the system was running strong:

I am correct to assume this is probably a pressure relief valve?

To replace the valve, do I just shut off the system, replace the valve, bleed it, then turn the system back on?

What specs do I need to consider when replacing it?

I started to watch Bob "Hot Rod" Rohr's video on pressure relief valves, but found it got advanced very quickly.


  • pecmsg
    pecmsg Member Posts: 4,909
    Just a bleeder valve to get the air out of the system.

    Now does this boiler have Glycol in it.
  • TonKa
    TonKa Member Posts: 104
    edited December 2022
    You might want to consider replacing those automatic air vents with manual vents, especially if you have an air separator at the boiler.

    Alternatively, if you still want the automatic vents for the convenience of filling the system, you could tighten the caps after the system is bled or even put a mini ball valve before them.
    JUGHNE Member Posts: 11,085
    You will have to drop the pressure (possibly draining most of the water or glycol out) below that point.

    I would go for the manual air vent myself.
    EBEBRATT-Ed Member Posts: 15,710
    Drop the pressure and unscrew the vent. If it goes bad remove the cap from the threaded pipe and install a reducing coupling and a straight relief valve.
  • hot_rod
    hot_rod Member Posts: 22,327
    I've never seen a side connection float/ auto air vent before?

    This is an easy replacement.
    Its both an auto vent, can be used manually. Or removed easily as it has a ball check built in. No need to drop pressure to remove or replace.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream