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Q - Hoffman #500

Alan_2 Member Posts: 28
I am draining a series loop baseboard convector system.
While the system is drained I am examining the various bleeder valves, about 10 of them.
Some of them seem to be automatic types, which I don't trust, especially in a 40-50 year old system.
Many of them have the copper green and white scale buildup around and underneath.

I came across a Hoffman 500, which seems to be a hygroscopic type but the inner screw is fused to the threads, thus unscrewing the upper half of the body and revealing the float ball.

I am inclined to go ahead and replace all the vents with the simple manual unscrew-to-vent types for the time being until next spring when the system will be re-configured for pumping away.

Any comments or suggestions would be appreciated.


  • DanHolohan
    DanHolohan Member, Moderator, Administrator Posts: 16,490
    These will get the job done.

    They're just slower to react the second time because the discs have to dry and shrink before the vent will react to air again. They've been around for a very long time.
    Retired and loving it.
  • Alan_2
    Alan_2 Member Posts: 28

    Thank-you, Dan -

    Replaced all the old Hoffman 500s with manual key types. There were seven total and all of them had serious scale buildup and green corrosion on the copper where the valves are mounted.
    This doesn't mean they are not working - I just went ahead and replaced them while the system was drained.
    I am going to clean off the scale and put them away just in case.
    Do they just act on their own as air gets near them ?

    It was fun refilling an old 1950s era two zone system that isn't pumping away.
    Plenty of improvising and tweaking as the water filled and air was burping/pushing out of various drains and manual bleeders.
    Maybe I shoud have kept the old vents.

    Thanks again.
  • DanHolohan
    DanHolohan Member, Moderator, Administrator Posts: 16,490
    All on their own,

    but a lot slower than a float-type vent.
    Retired and loving it.
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