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Uncooperative Buderus boiler

Alan80 Member Posts: 2
I have a Buderus G205 welded supply manifold that’s rusting out and would really appreciate suggestions from people with the experience of working through these problems. The pipe looks pretty weak, so I’d like to fix it ASAP before it becomes an emergency. (See picture.)

I tried to buy a new manifold from Buderus, but it’s no longer available, so my plan now is to just build it up with fittings.

I pulled the manifold by removing the four-bolt flange from the boiler. When I tried to remove the manifold from the flange, I wasn’t able to break the joint. We heated the flange with two MAPP torches for 5 minutes, put it in a vice and tried loosening the manifold using a 2 ft pipe wrench with a 5ft PCV pipe extension and it still wouldn’t budge. I was starting to twist the vice off the table, but the joint wouldn’t give.

So I put everything back together and the rusted joint is still holding. It dripped for the first hour or so, but seems to have stopped now.

I called Buderus and they do still have the flange available, but at $100+ and 8 weeks standard lead time. When I asked if it would really take that long, I was told ‘or longer’.

The flange looks to be a non-standard flange, with a square(ish) outline to avoid interference with the flue output. I believe the bolt circle is also larger than standard for a 1.5” NPT flange.

I can go ahead and order the new flange, but am concerned the manifold might not last that long.

Anyone have any suggestions for someone who might stock this flange?

If the pipe does start to leak and I need to fix it before the new flange arrives, any suggestions for getting the manifold out of the current flange without damaging it? I was tempted to cut some relief slots in the ID of the manifold and hammer it away from the flange, but was afraid of damaging the flange treads. If I am forced to fix it, is this the best approach? Would an oxy acetylene torch give me a better chance of heating it free? Any risk of cracking the flange with the higher temp? Should I just grind out the rusted section and weld the manifold closed in that area as a temporary fix? Any other thoughts?

It appears they used a blue, hard-setting sealant when the joint was assembled. It was also used in other fittings that were tough, but that I was able to get apart.

Again, I’d really appreciate any guidance from people with real-world experience solving these problems.



  • unclejohn
    unclejohn Member Posts: 1,833
    If there is a machine shop in your area take it there and they will get it off or make you a new flange. If not I have used a saw and carefully removed the pipe from the threads.
  • Paul48
    Paul48 Member Posts: 4,469
    You remove it in much the same way you remove a spud from a cast iron radiator, once the nubs shear off on you. Maybe this will help... https://www.youtube.com/watch?v=NpaezIzl3hg
    EBEBRATT-Ed Member Posts: 15,607
    The flange is cast iron and the pipe is steel. If you take the whole assembly off and bring it to a welding shop or an auto body shop or to someone who can handle a cutting torch they can cut the pipe out of the flange and save the flange in less than 5 min.

    Then you can rebuild the manifold with new fittings
    HVACNUT Member Posts: 5,860
    Try Marplat/Platzky Co. They're a Buderus/Bosch distributor.
    There on L.I. New York and if they can't get it for you, I don't think anyone can.
    If you have the I&O manual, have part numbers ready.
  • Paul48
    Paul48 Member Posts: 4,469

    I don't follow your train of thought. The cast will blow apart.
  • kcopp
    kcopp Member Posts: 4,439
    Honestly I would order the part.
    I have seen parts leak and hold out for long than 1 month.
  • Alan80
    Alan80 Member Posts: 2
    Thanks for everyone's help! If it starts to leak heavy before the new part gets here, I'll try the slice and chisel technique shown in the video. I've seen garages burn a bolt out of cast iron exhaust manifolds, but I don't know anyone I'd trust enough to not screw it up.
    EBEBRATT-Ed Member Posts: 15,607
    @Paul48 No, it won't blow apart.

    I have cut 100s of pieces of pipe out of cast iron pipe fittings and boilers and have never lost one yet.

    It's a lost less risky than using the sawzall/cold chisel method although I have done plenty of that in locations where I couldn't use a torch.

    Try it sometime. You have to really work to try and cut cast iron with a torch.....it doesn't want to cut. The torch will wash the steel pipe out of the threads leaving it undamaged. You heat the steel and stay away from the cast iron as much as possible