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Correct Type of Pipe for Steam Line?

We have a two-pipe steam system in our house (1918). The previous owner ran some galvanized on the steam inlet side of a radiator in a bathroom and painted it black, presumably to look pretty and match the painted water lines (to the sink). He never made the connection in the crawl space where the new pipe meets the original steam supply pipe.

What type of pipe do I use to connect the original pipe to the radiator? (This is a low pressure steam system.) The original pipe to that radiator is 3/4". It is painted silver with some interior corrosion, so I am not confident that I can determine what was the type of my original pipe.

What type of dope for the threads, or is teflon tape preferred?

Finally, the radiator tilts toward the inlet (steam) side. I don't think this is correct in a two-pipe system. Should I re-mount the small radiator (14" length), or does the pitch not matter much in a two-pipe system? This little radiator utilizes a wall hanger, so it will be more work than just putting some washers under the feet of a standing radiator. If the pitch does matter, what is the correct pitch for a radiator in a low-pressure two-pipe system?

Thanks,
Rod

Comments

  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,317
    Teflon tape with any pipe dope that is rated for steam is fine. Your original pipe is black steel (could be black wrought iron which I don't believe is made any longer) but black steel is fine.

    I don't believe the galvanized pipe will cause any problem. Usually cast iron fittings are preferred for steam but malleable iron is fine. The radiator should be pitched toward the return (low on the return end) but at 14" long you don't need much pitch.

    The supply should come off the main from the top or on a 45 and pitch up toward the radiator. The return should come off the radiator trap and pitch down toward the return main. You don't want the supply or return branches to have any pockets to collect water
    ethicalpaul
  • Fishin_Rod
    Fishin_Rod Member Posts: 20
    Ed,

    Thanks for the help. I didn't know I was supposed to use a belt and suspenders (tape & dope) on my connections. Do you think the fine print on big box store pipe dope will say if it is steam rated, or do I need to go to a specialty store?

    After posting, I found a note that galvanized pipe is not used for steam applications because when the zinc coating finally starts flaking, it could plug the system. I think I will take out the three pieces of galvanized pipe.

    The original steam supply line is sagging - I assume because it was disconnected. Can I plumb it back in correctly by using only vertical sections and horizontal sections that are perfectly level or are sloped slightly back towards the boiler?

    Thanks,
    Rod
  • Fred
    Fred Member Posts: 8,542
    You want to slope those pipes back towards the main and you can pull them up with the vertical pipe but if those horizontal pipes have sags in them, you need to try to lift those sags out with some additional hangers.
    Most of the big box stores sell name brand pipe dope and the containers almost always have temp ratings on them.
  • Fishin_Rod
    Fishin_Rod Member Posts: 20
    Fred,

    Thanks for the advice. As a novice, I see I incorrectly used the term sag. The disconnected pipe is not anchored properly, so the elbows on the two horizontal segments are lower on the side "away" from the main. I used "sag" as a shorthand for that condition.

    When I replumb, I will get them sloped the correct way.

    I have noticed that the long pipe runs in my basement do have hangers. I will inspect these for true "sags" the next time I get the chance. Despite my admonitions, my wife will frequently hang 80 pounds of laundry on the overhead pipes. (I got her off of the gas line, but I think she may have started hanging things on the condensate return line.)

    Rod
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,317
    You can use tape or dope or both together. Teflon makes it go together easier. Pipe dope seals better most think. Personal preference.

    As @Fred mentioned pitch is important.
  • Fred
    Fred Member Posts: 8,542
    Not a good idea to put weight on any of the steam or condensate pipes. A sag can occur, over time and create sections that will sag, allowing condensate to pool in those areas and then water hammer will likely occur if they are in areas where steam gets to that pool of water. Even if steam doesn't get there, pools of water in those pipes can eventually cause pin holes from rust through..
  • Mustangman
    Mustangman Member Posts: 9
    Here is what I came up with over the years. Tape alone works okay, dope alone works okay. 3 laps of tape and dope on the first 2 threads is great. I hate sloppy pipe dope smeared all over. If you just use it on the first few threads, the dope will roll back as you tighten the joint. You end up with just a ring of dope that looks like a professional did it. Hey... thats what we are!
    Neild5