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Assembly Question!

Robbie Member Posts: 41
Happy New Year, Steamers!

I have FINALLY reached the boiler assembly stage after a good month of working on the house, and have just assembled all the close piping. I used pipe dope liberally on all the threads for the pipes, but have a question... When I assemble the unions, should I be putting a little pipe dope on the faces of the cone and cup, or the outside flat parallel flange area, or the union nut threads, or anywhere besides the pipe threads? 3 of the unions(2 - 2", and 1 gas line) are the original ones, and have a little wear: the fourth is brand new. I am not experienced with plumbing, so I figured I would ask...

For those following the work, I have been trying to get to this point for about a month: since I am not living in the house yet, heat has not been a real issue: but with the recent cold snap in the idatlantic, it has been quite chilly working in the house, so I finally put everything else aside & decided to push getting the boiler assembled, radiators in, and steam up...

Waiting for a reply! I will post pics when I am done-




  • jpf321
    jpf321 Member Posts: 1,568
    and while we are on the subject....

    i have heard that teflon tape is a poor choice in steam piping...is this true?

    what is the best pipe dope to use?

    i've seen alot of pictures that use blue dope .. some that use white .. is there a best practice dope out there?

    thanks & HNY
    1-pipe Homeowner - Queens, NYC

    NEW: SlantFin Intrepid TR-30 + Tankless + Riello 40-F5 @ 0.85gph | OLD: Fitzgibbons 402 boiler + Beckett "SR" Oil Gun @ 1.75gph

    installed: 0-20oz/si gauge | vaporstat | hour-meter | gortons on all rads | 1pc G#2 + 1pc G#1 on each of 2 mains

    Connected EDR load: 371 sf venting load: 2.95cfm vent capacity: 4.62cfm
    my NEW system pics | my OLD system pics
  • Unknown
    edited January 2010
    Assembly Pipe to Fittings.

    The idea of using dope or teflon tape is lubricate the joint to reduce friction so you are able to get the tapered threads tighter to get more and deeper metal to metal contact.  Any sealing of the joint is secondary to that purpose and is to stop possible spiral leaks. While I'm not that up on the latest pipe dopes, I've always used RectorSeal #5. You want to make sure your threads are clean, then dope the male threads, give it a wrap or two of teflon tape and then dope the female threads of the fitting and then carefully screw them together.

    As to your question on unions- Generally you don't want to use anything on the flange faces. Just make sure they are clean and have not "dings". Use dope of the threads as those are have you want to have tight. If I have a troublesome union I use teflon tape on the face and this sometime works. (It isn't to code) After that I chuck the fitting and use another one.

    Happy New year!

    - Rod
  • David Nadle
    David Nadle Member Posts: 624

    This topic has come up before and there's no definitive answer. At the risk of sounding like a dope myself, as I'm certainly not a professional pipefitter, I'll share that in my limited experience, dope with teflon (the white stuff) that stays pliable works just great, especially for things you might have to take apart again. Dope that cures rock hard (the blue stuff) works too, but it's harder to get stuff apart. For things you might take apart every season, like a skim port or a plug to add chemicals, teflon tape works fine.

    I've always used only tape or dope, never both, and I've always doped only the male threads, and it's always worked (beginner's luck?). The important part is to get the right number of turns in. You shouldn't put anything on the face of a union. If it won't seat you should get a new one.  
  • Steamhead
    Steamhead Member Posts: 16,894
    I like to use

    anti-seize on the union nut threads. This helps tighten it, and makes it easier to loosen it later if needed.

    With some of the crappy threads we've seen lately, especially on 2-inch and larger pipe, we'll use Teflon tape and red hi-temp RTV silicone caulk. This has proven to be very reliable, and is still easy to take apart if needed.
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
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