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Rongold Member Posts: 19
edited November 2021 in Plumbing
Hi all,

I did some work on my boiler over the summer and installed 2 new Caleffi air vents with the check valve under them. Supposedly, the check valve will allow you to remove an old vent valve and install a new valve without the need to relieve the pressure in the system or drain the system down. I have a couple of spares and was checking them out, but the check valve does not seem to close fully until the vent is completely unscrewed and removed. It appears that the check valve is open for a split second while you are unscrewing the vent, and actually closes as you remove the vent, which would allow liquid to escape and possibly burn you. I have enclosed a few pictures--One with the vent screwed in, and a couple with the vent just about unscrewed all the way and another with the vent removed showing the check valve closed. Have any of you actually tried to replace a vent when there is a check valve installed, and did it work properly ???

The first pic shows the 2 pieces.

The second pic shows the vent about 1/32 of a turn from being removed, and if you look close the check valve is still slightly open.

The third pic shows the vent screwed into the check valve as it would be when installed in the system showing the check valve open.

The last pic shows the check valve in the closed position with the o-ring seated & sealed. The valve doesn't actually reach this position until the vent is totally removed. Even if the vent is 1/8 turn before removal, that o-ring IS NOT seated. It seats as you lift the vent out of the check valve.

Do these check valves really work ???



  • Zman
    Zman Member Posts: 7,125
    Not sure why they wouldn't.
    @hot_rod ?
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • Yes, they work as long as the o-ring doesn't get fouled.
    Often wrong, never in doubt.
    JUGHNE Member Posts: 9,292
    So the air vent itself, as it is screwed in, depresses the internals to open the check valve? Just like a Schrader on AC fittings? What a country!

  • hot_rod
    hot_rod Member Posts: 15,410
    Move fast!  Yes for a split second it could spit if you are slow to the rotation. As @JUGHNE mentioned it is similar to a tire stem, or basketball needle, or Pete’s plug, etc
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream