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Leaking copper tube...custom or off the shelf part?

Hi everyone and Happy almost new year!

First post on this site but have been a long time reader...between this site and the "Lost art of steam heating" book I have managed to replace/upgrade/tweak a ton of stuff on our steam heat setup.

"Recently" I sprung a leak on a small copper pipe on the boiler itself. The pipe runs from low water cutoff to the pipe that runs from the top tube of the sight glass. I attached a picture but cant seem to find what this part would be called or if it is even an off the shelf part at all.

Boiler is a Crown JBF52EID

Any help would be appreciated!




  • Jamie Hall
    Jamie Hall Member Posts: 22,918
    I'm sure there's a special name for it... but there's no good reason you can't make your own. Soft copper tubing of the right size, looks like compression fittings but you can double check that. I'd use a tube bender, though, to bend it because the stuff is so easy to kink.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • EzzyT
    EzzyT Member Posts: 1,290
    We typically rip that soft tubing and compression fitting out and just replace it with 3/8” brass fittings and nipples.
  • jerryb46
    jerryb46 Member Posts: 59
    that tube is made of brass and is called l vent on a mc donnel-miller low water cut off.Can be brought at a Plumbing supply that has heating supplies,boilers, heating controls,etc.
  • Steamhead
    Steamhead Member Posts: 16,726
    The McDonnell & Miller part is rather cheesy. I don't think it's real brass. @EzzyT 's idea is good, as is @Gordo 's which will also work on a #67:


    We prefer the Hydrolevel setup since it has no moving parts.
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    EBEBRATT-Ed Member Posts: 15,323

    That tubing is part of the McDonnell Miller low water cut off kit. I don't know if its available as a separate part.

    It is 1/2" OD tubing. I would find a piece of 1/2" od tubing (hard or soft) cut the old tubing out and replace it with new. Save the fittings .

    You need: 1/2" od tubing
    1 1/2" od sweat or compression 90 degree elbow (if you don't have a tubing bender)
    2 1/2" od compression sleeves