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New Air Vent at highest point in system NOT venting


We had a new air vent installed at the highest point in our hot water radiant heat system. The old vent wasn't venting and we were concerned about trying to open it so a new one was installed. It has not vented ANY air since it was installed during a repair. Is this normal?

The air vent near the boiler itself vented air for a few days after this same repair and I expected more air to vent at the highest point. The height is 17 feet and the boiler is reading 16psi right now so it should be more than sufficient for the height.

We do still hear water running when the system comes on in the night, not as bad as before the repair so I know the air released from the vent near the boiler has helped but I feel there is more in the system near the upper radiator.

Any thoughts? Could the piping leading the the vent itself be plugged?

Picture attached for reference - excuse the terrible paint job by the prior owner :)



  • neilc
    neilc Member Posts: 2,707
    anything's possible,
    been a run of bad pressure gages today , , ,

    turn the boiler off so the circs stop,
    try SLOWLY unscrewing that vent from it's pipe and see if there's water under it, don't unscrew it all the way, but til it loosewns up, and you should see water come thru the threads,
    if you don't see water, your boiler pressure is low, and that gage wrong,
    known to beat dead horses
  • hot_rod
    hot_rod Member Posts: 22,251
    What type of air purger is back at the boiler?
    got enough flow? You want at least 2 fps, if you have a multi speed circ, try a higher speed for a day 
    If the air is going around, the purger at the boiler should be doing most of the work.

    High point vents grab air that migrates up when the circ it off.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • JustJenn
    JustJenn Member Posts: 4
    Neilc- thanks for the troubleshooting suggestion. I’ll consider that for a warmer day!
    hot_rod - I’ve attached a photo of the vent at the boulder as well as the new pump which is set of High.