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Cast iron fittings and black iron fittings

ac62002 Member Posts: 1
How can you tell if it is a cast iron fitting or a black iron fitting? I have several mixed fittings in a container; I need a few black iron fittings to extend the gas line in my basement.


  • Gilmorrie
    Gilmorrie Member Posts: 185
    Common "black iron fittings" is a misnomer - they are ASTM A53 steel, the same as galvanized fittings except they are uncoated. They are normally machined and often threaded. Their black color is because of shop painting. Cast iron plumbing fittings are usually used only for larger fittings and show signs of being cast and typically not machined.
  • mferrer
    mferrer Member Posts: 33
    Black cast iron fittings appear thicker. There hubs are wide and there exterior is relatively smoother than black malleable fittings which appear to be sleeker, have thin hubs and have a kind of sandy finish.

    Black malleable is used for oil and gas and cannot be cracked or busted with a hammer making then safe for the application. On the other hand, black cast iron fittings can be broken with a hammer and unsuitable for said applications. They are used for steam and water systems.
    EBEBRATT-Ed Member Posts: 15,623

    Sorry to be this way but working on gas can be dangerous. If your not qualified (and not knowing about the fittings suggests that) you shouldn't be fooling with gas.