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Expansion tank piping device


The expansion tank taps into the system thru an unusual device. Does anyone know what this device does? Could it be a regular tee with a clean out at the bottom? This is about 15’ away from the boiler on the supply side of a hot water system. There is evidence that this system was converted from steam. House is 100 years. Tank is 12” x 48”. Thank you


  • leonz
    leonz Member Posts: 1,187
    You have a steel compression tank and when they plumbed it in apparently they tapped in the main line to fill it.

    Would you please post more pictures of the boiler plumbing and the circulators please.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,167
    edited February 2021
    That appears to be a Schedule 80 Tee. ...or it could just be a Cast Iron Schedule 40 reducing Tee made from a larger diameter reducing Tee blank where the smaller "thru" openings were drilled and tapped for the smaller pipe size. I don't think it is any special fitting for an expansion tank. After the system was converted from an open gravity system. to a closed system the expansion tank was added by drilling and tapping a 1/2" pipe opening in the existing tee.

    You will never know what they were thinking when that was done. The guys that did that are all Deadmen now.

    Is it possible that the bottom of that Tee is where the original Coal Boiler was located and that is where one of the risers from the boiler was piped in? When a replacement boiler was installed the new boiler is moved closer to the chimney and the old opening was just plugged up.

    This is where I love to try to figure out what was where... by the way the basement floor concrete is resurfaced, where a coal bin and coal shoot might have been, and how the replacement was designed by the different fittings and pipe sizes used. I remember looking at an old church and seeing how they redesigned a one-pipe steam boiler in a basement to a boiler located above the basement in a boiler room built on the parking lot about 12 feet higher than before. The boiler in the basement flooded and they had to redesign everything to PUMP the return water from the basement UP into the new boiler room location using a condensate return system.

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

    EBEBRATT-Ed Member Posts: 15,840
    They put in a larger tee to slow the water down. An air scoop of sorts except the expansion tank pipe should have come out the top instead of the side
  • Subtle Steam
    Subtle Steam Member Posts: 3
    Thank you all for your great comments. The “new” boiler is in a different spot with another expansion tank above it.
    There is a very good chance that an earlier supply piped into the bottom of that tee. I will look closer at the floor.
    The side tap was, unfortunately, the only option with the clearance to the tank. I am unable to obtain further photos.
  • mattmia2
    mattmia2 Member Posts: 9,962
    If the tap came off the top of the tee then went down to the tank, the air would still tend to collect in that pipe and migrate to the tank.