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Mixing copper and iron pipes for steam? Insulation?

SethK Member Posts: 43
I bought a 150-year-old fixer-upper and a few steam pipes need to be re-routed. I looked at getting some iron pipes at Home Depot, but it is many times more expensive to get iron pipes threaded than it is to buy copper -- I think they wanted $10/ft for iron pipe if I got a custom length threaded.

I have experience with copper pipe, is there any reason I can't use that for some steam pipes? I see mixed answers online and in this forum posters seem to have deleted their original questions so it's hard to understand the answers.

Would there be a chemical reaction between the metals? Would I need to use connections that keep the different metals from touching? If so do I need to connect them electrically or do I want them isolated? Would it do bad things to the water or the boiler to use copper and iron?

Details: 1 pipe steam, boiler is only 3 or so years old. All of my steam pipes are exposed, so even if I did a bad soldering job (never!) it wouldn't be a big deal to fix. The pipes that need replaced are most of a riser to one radiator and a segment of one return line currently running dead-center down the basement at forehead height..

Also, none of my pipes are insulated. Should that be a priority? Which pipes should be insulated? Thanks!


  • Jamie Hall
    Jamie Hall Member Posts: 18,946
    Um... well...

    Let's get the easy one out of the way first: all steam carrying pipes should be insulated wherever they are accessible.  One inch is best.

    Copper is not generally recommended for steam lines.  The problem isn't electrolysis -- there shouldn't be any liquid water sitting in a steam line to cause a problem.  The problem is expansion.  Copper expands a lot when it goes from room temperature to steam temperature, and if the expansion is resisted the forces can be tremendous.

    However... if you are very very clever with your pipe routing -- always keeping in mind that the water has to drain back to the boiler, and the pipe sizes have to be adequate and the pipes pitched properly -- you can get away with copper if you don't mind the expansion noises.  Keep in mind as you plan the routing that the pipe lengthens as it heats up, and that lengthening has to have somewhere to go without restraint.  In larger sizes -- such as have to be used for steam lines! -- you will need expansion loops, and the legs of the loops will have to be at least 2 feet long for every inch diameter pipe to be safe.  Never set the piping up so that expansion can put a torque on a joint.  It will fail over time.  And I could go on...

    On second thought... it's a whole lot easier, and in the long run it will be a whole lot cheaper, to run the thing in threaded black iron, as it should be done.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Bio
    Bio Member Posts: 278

    You can purchase the whole length of pipe which is cheaper, have it threaded and with the left over you can come back and just have sized, threaded and pay for the thread job only
  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,564
    edited May 2014
    rerouting steam pipes

    Why not tell us about the changes you wish to make to the pipes. Rerouting requires thought as the piping must follow certain principles. if not, you may have water-hammer.

    the insulation must be fiberglass, and not any sort of plastic foam, as it will melt.--NBC
  • JStar
    JStar Member Posts: 2,752

    Just don't do copper. If you ever saw the things that we do, you wouldn't even consider it. The copper WILL destroy the rest of the iron in the system, even with dielectric isolation. Add the years of leaks and noises, and it's just not worth it. If you are anywhere near NJ, we can cut and thread custom pipe for you.
  • KC_Jones
    KC_Jones Member Posts: 5,081

    I am not going to put prices, but I have been looking at this a lot lately.  I am trying to get my budget worked out for my steam boiler replacement.  Not sure what prices you are getting, but the prices I am getting the black pipe is WAY cheaper than equivalent copper pipe pipe.  Also I haven't seen a home center that even stocks copper in the sizes I would need on my steam system.  Maybe I am the crazy one?!  I am working with a local plumbing supply house.  Are you replacing pipes because of leaks or because you want to move them?
    2014 Weil Mclain EG-40
    EcoSteam ES-20 Advanced Boiler Control
    Boiler pictures updated 2/21/15
  • Snowmelt
    Snowmelt Member Posts: 1,334
    Kc jones

    I don't like the word budget or cheaper when we are fixing or updating heating equipment , I was listening to a webinar on return on evestment. As soon as someone says I have a budget and what's my return on investment or I'm being cheap there is really nothing we can do in this field except say heating systems are like pigs, they eat oil and gas, then spit out btu's all we can do as cheating professionals is put that pig on a low carb diet so it produces the best btu at a minimum amount of carbs (carbs being oil or gas)

    Did I say that right.
  • KC_Jones
    KC_Jones Member Posts: 5,081
    budget etc.

    I am doing my own work so the "budget" is being dictated by the proper work not the budget dictating the work I do.  I am just trying to figure out how much I am going to need to buy all the components to do it correctly.  I am do it right regardless of cost kind of person.  My basic point to the original poster is they may want to evaluate the cost that they are seeing because I am see something different.  Copper is automatically more expensive than steel just for the raw material so I was confused by the statement that black pipe costs more because I am just not seeing that on my project.  Another thing to consider is long term expenses.  What will happen long term with the copper versus the black pipe?  Sometimes it's a pay me now or pay me twice later kind of scenario.  Short term gain for long term loss.  Personally I like to do things once and then not worry about it, usually ends up being cheaper that way.
    2014 Weil Mclain EG-40
    EcoSteam ES-20 Advanced Boiler Control
    Boiler pictures updated 2/21/15
  • vaporvac
    vaporvac Member Posts: 1,520
    Cost for threading!

    I'm not sure what you're doing, but Home Depot  threaded my pipes for free on my recent install! (Or maybe it was Lowe's)  I just bought the long solid pieces and they cut and threaded them. Of course, that was only on the smalle pipes as they only stock and thread up to 2".  We had to rent a threader for the 3 and 4 in pipe.   It not that hard to thread smaller pipe if you have a lot of it to do, but check out Lowe's if HD really charging. Colleen
    Two-pipe Trane vaporvacuum system; 1466 edr
    Twinned, staged Slantfin TR50s piped into 4" header with Riello G400 burners; 240K lead, 200K lag Btus. Controlled by Taco Relay and Honeywell RTH6580WF
  • jumper
    jumper Member Posts: 1,839

    Every time this topic arises I wonder why XXIst century chemistry doesn't sell some sort of stuff to join steam pipes. We're talking about minimal pressures here.
  • Snowmelt
    Snowmelt Member Posts: 1,334
    Minimum pressure

    Yes but very high temp, I believe above boiling because that's how we creat steam.

    I do have a question, I'm a huge viega press guy, my supply house that has both mega press and copper press tells me it really not going got make a difference with the press , says I could use either copper or mega press, just a preference on what you feel comfortable with as an installer.
  • SethK2
    SethK2 Member Posts: 1
    edited May 2014
    Me again

    My account seems to have been locked or deleted so I made a new one (edit: nope: I'm a moron and the emails were in my spam folder...)

    First: a question on insulation:

    Should I insulate the return pipes as well, or just the steam pipes? Won't steam travel down the returns until it hits the main vent?

    I have never seen insulation on an exposed riser before, I guess that's because it's in conditioned space?

    Now to answer some questions:

    On riser went straight up through my kitchen in a spot that was fine when there was a wall there, but now that the wall is gone it needs to be moved a little to be against another wall.

    The return travels from the end of the main, paralleling it back to the boiler down the center of my basement at forehead height. I'd like to route that along the basement wall.

    HD was charging me by the foot for threading pipes, even though that makes no sense at all, which is why iron was more expensive. I.e. threading two ends to a 10 foot pipe costs 10x the price of threading two ends of a 1 foot pipe. I like that idea of buying a pre-threaded pipe, taking it home to cut it, then bringing it back for threads. Maybe I can skip some driving by asking them to cut it after I pay for it, then pay for the threads.

    Sadly that won't work for a riser as I need 12 or so feet, so I think HD wanted $120 for that one pipe. I will look around the Boston area for other sources. Maybe I need to try Lowes, or maybe the person I talked to at HD was a moron and I need to try again.

    I'm definitely getting mixed answers on if copper is bad for the iron when mixed, but it seems like I should go iron. I just don't think that's possible with the riser...

    Thanks again for all the help!
  • KC_Jones
    KC_Jones Member Posts: 5,081
    copper with iron

    I don't think there is much argument on if the copper will eat the iron because it will.  See attached picture of a simplified galvanic chart.  The iron/steel is more susceptible to corrosion than the copper so when the 2 come in contact the iron will be sacrificed, there really isn't any way to argue that point.  The bigger problem as was pointed out earlier is the expansion of copper versus iron.  The copper expands at a much greater rate than the iron so that is what would be of primary concern.  This will stress the solder joints (regardless of how good the joint is).  I would agree the person you talked to either didn't understand or doesn't know what they are doing.  Cutting threads doesn't care about pipe length.
    2014 Weil Mclain EG-40
    EcoSteam ES-20 Advanced Boiler Control
    Boiler pictures updated 2/21/15