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Easy question - Valve Replacement (‘48 system)

Hey folks!

Trying to narrow down the issues with why boiler needs water added daily - starting with replacing a few leaking air valves. 

The guy at Home Depot told me this would fix both styles below but A) I don’t trust 90% of their employees and B) the previous owners hacked everything they touched so I’m not sure how off the system is just going into it.

I tired the valve on one and it didn’t work (no steam would go through at all) is that because it doesn’t have the little tongue thing that was in the original? 

I’m sure this is an easy one for you all, but I want to learn. Dad said I should have been a plumber and he was right. Thank you for any and all direction!



  • Jamie Hall
    Jamie Hall Member Posts: 23,310
    Well, @margopenelope , it's never too late to learn...

    The little tongue thing is there to allow any water droplets to get back into the radiator where they belong. Any quality vent of that type will have it. Home Depot vents aren't quality.

    The round vent in the first picture is a Gorton; which one it is will be marked on it. If that convector heated adequately and didn't bang, that is what I would replace it with. Amazon has them.

    Now to adding water daily. Unless you have a vent which is really truly stuck open -- which you will know because, first, the radiator will be nice and hot and second there will be evidence of dampness near the vent (if not sure, drape a paper towel over it) -- it's unlikely that you are losing that much water through the vents.

    That is not good news. You need to see if you an find any evidence of a leak somewhere. Do you see billows of white "smoke" which dissipates in a few tens of feet coming out the chimney? Not good. Do you have piping which is below the water level in the boiler? Can you check that for leaks?
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Big Ed_4
    Big Ed_4 Member Posts: 2,785
    The return from the main , does it run under the slab ? Is the water in the gauge glass clear ?
    I have enough experience to know , that I dont know it all
  • BobC
    BobC Member Posts: 5,478
    edited November 2020
    In your second photo there is a Ventrite with what looks like a USAV Home Depot vent. The Ventrite is as good a vent as you can buy while the USAV is at the bottom of the heap.

    New Ventrite's are not cheap, if you don't want to stretch that far Gorton or Maid O Mists are good and they cost less. The maid O Mist I use is the 5L. that comes with 5 orifices in the box so you can select the veting rtate by screwing on a different size orifice.

    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • nicholas bonham-carter
    Now is the time to do the overfilling test-up to the header, where you can feel the cold, and let the boiler sit for a couple of hours. Water on the floor, or in the fire box indicates a leak in the boiler it self. If the level drops, without water underneath, It points towards a leak in any buried wet returns.
    When you have done the test, and noted any results, post them here for further advice.
    Where are you located?—NBC