Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

Steam boiler

Spag74 Member Posts: 16
edited September 2021 in Plumbing
Which is best to use when piping  a steam header connection a regular union or a cast iron flange union w/a gasket?
2” header pipe and it will be located on risers out of the boiler 


  • Steamhead
    Steamhead Member Posts: 16,469
    What pipe size? Where in the header will it go?
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    EBEBRATT-Ed Member Posts: 14,543
    Either one is fine but I would lean towards a flange union on 2 1/2" and up but neither is wrong.

    If you have a 4" union you need a pretty big wrench to tighten the nut and a big wrench to hold back on it.

    A flange union only needs wrenches for the bolts which may be an advantage in some cases
  • mattmia2
    mattmia2 Member Posts: 8,874
    Even if you have to cut the bolts on the flange at some future point it is still easier than cutting apart a fitting and all you will have to do is replace the bolts to put it back together.
    JUGHNE Member Posts: 10,909
    edited September 2021
    A 3"union needed my 36" fully open for the nut and a 24" fully open for the fitting.
    Cheater pipes on each and 2 people with minor grunting.

    For 4" I used flanges with gaskets.
    JUGHNE Member Posts: 10,909
    For 2" it seems to me that regular unions would be my choice.

    2" header with two 2" risers.....what does the install piping diagram show?