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Steel pipe sweated to copper fittings?!

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  • Steel pipe sweated to copper fittings?!

    I looked at a heating system boiler replacement job today and observed what appeared to be emt sized steel pipe soldered into typical 1/2" sweat copper fittings.

    Wondering if it was copper pipe with a coating or plating on it for some reason I scratched some of the pipe and it was indeed steel. There's also rust here and there. A magnet also stuck to the pipe.

    I've heard it can be done but have never seen steel pipe and copper soldered together before. The joints have held the dissimilar metals since the house was built, and judging from the boiler it wasn't built last week.

    Who knows, in a really competitive bid situation maybe I can just go to home depot buy some emt and install that instead of type M or L.
    Attached Files
    Time flies like an arrow.

    Fruit flies like a banana.

  • #2
    Re: Steel pipe sweated to copper fittings?!

    closed system and probably has some chemical in it. plus it lacks oxygen and without oxygen, it stops rusting. rusting is short for oxidation.

    look at all the fire sprinkler and large bore heating chilling lines. all steel.

    with the proper flux, you can solder dissimilar metals.

    rick.
    phoebe it is

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    • #3
      Re: Steel pipe sweated to copper fittings?!

      I'd be glad to give ya some tips on bending emt with a bender. Might save ya from sweating those 90's.

      Huck

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      • #4
        Re: Steel pipe sweated to copper fittings?!

        I use Harris stay-brite 8 to join copper and steel tubing.

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        • #5
          Re: Steel pipe sweated to copper fittings?!

          Originally posted by James P View Post
          I use Harris stay-brite 8 to join copper and steel tubing.
          Just curious, where do you get steel pipe sized to fitting 1/2" sweat copper fittings?
          Time flies like an arrow.

          Fruit flies like a banana.

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          • #6
            Re: Steel pipe sweated to copper fittings?!

            Originally posted by PLUMBER RICK View Post
            closed system and probably has some chemical in it. plus it lacks oxygen and without oxygen, it stops rusting. rusting is short for oxidation.

            look at all the fire sprinkler and large bore heating chilling lines. all steel.

            with the proper flux, you can solder dissimilar metals.

            rick.
            Yep to all, I just thought the mixed material aspect was unusual, and other than EMT I haven't seen steel pipe that size.
            Time flies like an arrow.

            Fruit flies like a banana.

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            • #7
              Re: Steel pipe sweated to copper fittings?!

              That's what You get when sparky does plumbing. Check the elec. panel, Probably all copper L . After seeing the romex
              Iknow the elec. out fit . " WE WIRE FOR FIRE !! "
              Last edited by toolaholic; 10-13-2010, 09:03 AM.
              I can build anything You want , if you draw a picture of it , on the back of a big enough check .

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              • #8
                Re: Steel pipe sweated to copper fittings?!

                Originally posted by geno gardner View Post
                Just curious, where do you get steel pipe sized to fitting 1/2" sweat copper fittings?
                Don't know about steel pipe. About all I've sweated was steel compressor stubs to copper.

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                • #9
                  Re: Steel pipe sweated to copper fittings?!

                  Originally posted by James P View Post
                  Don't know about steel pipe. About all I've sweated was steel compressor stubs to copper.
                  I'm going back to the house to do a heat loss to see if it's feasible to install a smaller boiler to save the HO some money.

                  I noticed on the first trip the original boiler fill line was steel that has been disconnected, and a new line installed elsewhere. While I'm doing the heat loss if I can get at that line (It's sort of buried) I'll cut off a piece and then we can get some dimensions to see what kind of steel pipe it is.

                  It's probably not important, I'm just curious.
                  Time flies like an arrow.

                  Fruit flies like a banana.

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                  • #10
                    Re: Steel pipe sweated to copper fittings?!

                    I'm surprized more people here are not interested in your bizzarre findings.... please post more info as you get it!

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                    • #11
                      Re: Steel pipe sweated to copper fittings?!

                      I find it hard to beleave any plumber would use any type of galvanised or any type of iron pipe for conveying hot water as it will rust up in a vary short period of time that is why copper has always been used.

                      Tony

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                      • #12
                        Re: Steel pipe sweated to copper fittings?!

                        go ask this ?? on heating help.co I think i remember talking to a old timer boss i had that this was make for that due to copper scares I think jeff

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                        • #13
                          Re: Steel pipe sweated to copper fittings?!

                          Looks like stainless steel to me

                          One of my customers worked for a water treatment plant back in the '60's. His whole house was piped in stainless with copper fittings. Said the plant had hundreds of feet of 'leftover' pipe that wasn't being used so he took it home and installed it when he cut out the galvanized.

                          His fittings were brazed not soldered but I'll bet it could be done with the right flux and solder.

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                          • #14
                            Re: Steel pipe sweated to copper fittings?!

                            Originally posted by plumberscrack View Post
                            Looks like stainless steel to me

                            One of my customers worked for a water treatment plant back in the '60's. His whole house was piped in stainless with copper fittings. Said the plant had hundreds of feet of 'leftover' pipe that wasn't being used so he took it home and installed it when he cut out the galvanized.

                            His fittings were brazed not soldered but I'll bet it could be done with the right flux and solder.
                            It's steel
                            Attached Files
                            Time flies like an arrow.

                            Fruit flies like a banana.

                            Comment


                            • #15
                              Re: Steel pipe sweated to copper fittings?!

                              Soft soldering steel to brass or copper isn't unusual in the industrial world, but there is a little technique to it. Many common acid fluxes will work fine. I personally have not tried regular water soluble plumbing flux. The free iron on the steel surface will oxidize quickly so it's best to mechanically clean the steel right before soldering - just like copper, except the steel is a little harder to clean. If the steel is galvanized, you have to get the zinc off. I've never gotten it to work with leaving the zinc there. Most of the time it turns white (zinc oxide) and you end up with a mess.

                              The only problem with the actual soldering is that steel has a much lower thermal conductivity than copper - it's about 1/6 to 1/7 as conductive as most coppers (depending on alloy). The result of this is that the steel part will not conduct heat away from the joint as fast as the copper part will. Since the heat doesn't conduct away very quickly in the steel, the steel has a tendency to get too hot and burn the flux before the copper is hot enough. So you usually have to use a lot of flux on the joint to keep it wet, , wrap a wet rag on the steel a foot or so from the joint, and preheat the copper pipe for a foot or two with the torch. Then, heat with the flame on the copper side.

                              Stainless is tougher but still possible. I've never soft-soldered stainless to different metals or even to itself... I've used silver solder and and oxy-acetylene torch. The thermal conductivity of stainless is much less even than regular steel (about 1/3 of the thermal conductivity of steel) so burning the flux can be a real problem... and as you know, once that happens, you take it all apart and start again.

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