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Recommendation for Main Repair

4Barrel Member Posts: 125
I'm considering a 2" main repair; the section is at the end of the main - see pics. The system has been losing water, and this seems to be the place where it's happening... the last section of the main and the last two 1-1/2" run-outs appear to be rotten. (Insulation was added a just few years ago. I removed it for these pics.)

My plan was to cut the main back about 2' from the last T (where a wrap repair had been attempted), and re-thread using a manual threader. The main is about 7' above the floor, and I have about 3" clearance from some copper piping that runs alongside the main. My local tool rental shop has a 4-wheel cutter that should allow me to sever the pipe in its current position. (I'll need to sawzall the run outs since they weren't installed with unions...)

The other option is to attempt removal of the main back to the closest junction, a T about 12' closer to the boiler. This section runs through two masonry walls, and would be challenging to pull out and expensive to reinstall new.

I suppose if the threading fails, I could then proceed to removing the big section, but I’d rather just pick the right approach to begin with. Thoughts, input, recommendations are welcome and appreciated.



  • rusty piping repair

    i would be worried that any pipe which has rusted out will not resist the torque of re-threading. therefore i would replace the whole length back to the next fitting.

    you can cut the pipe close to the fitting, and then make some radial cuts, to be able to collapse the stub inwards, in the fitting.

    anchor the pipe at both ends of the section to be replaced, so it will not move out of pitch/alignment. use some unions, so if next year you are replacing an adjacent section, it will be easier.--nbc
  • 4Barrel
    4Barrel Member Posts: 125
    tough spot

    thanks NBC. i should have included in my earlier post that the location of the next fitting 12' away is right next to a masonry wall, making your recommended approach that much more of a challenge (see pic)... it's a tough spot to make the cuts you suggest. so i think i can only hope that enough heat and torque will release that fitting. the flip side of re-threading is problematic too, as you point out. ugh. am i missing something? is there another approach?
  • Hap_Hazzard
    Hap_Hazzard Member Posts: 2,849
    This was avoidable

    The piping was not hung properly. You always need to support the fittings as well as any spans greater than 10 ft. in length. The fittings being heavier will create a sag where condensate will collect, so you have water in contact with steel in the presence of abundant oxygen at the weakest part of the pipes, where the threads are cut halfway through the walls.

    Since the destruction is probably localized, you might be able to get away with replacing only the damaged parts, but you need to think in terms of where the water has been lying in the pipes and how deep. Then start cutting.

    Before you start putting things back together, get your hands on a borescope and use it to survey as much of the remaining piping as you can reach, and make sure you can get a look at any other low points that haven't rusted through yet. Keep in mind that things have been changing over time, as unsupported sections will sag more as they rust and weaken.

    Whenever you thread pipes in place you risk damaging the end opposite the free end you're threading, so mark the pipe and fitting so you can tell if the joint has rotated. If it does you need to unscrew the pipe, inspect the treads on the pipe and the fitting, and apply new joint compound.

    Since you're going to be needing a lot of unions, these will need to be supported too, so you'll need to buy a lot of new hangers. These should be either clevis or split-ring hangers suspended by 3/8" or greater threaded rod. Perforated strap is not acceptable.

    You should consider getting the hangers first so you can use them to stabilize the pipe while you're working on it. This helps minimize potential damage to the rest of the piping, but this is always going to be a risk no matter how careful you are. You're going to be applying considerable force to aging piping, and everything is connected.
    Just another DIYer | King of Prussia, PA
    1983(?) Peerless G-561-W-S | 3" drop header, CG400-1090, VXT-24
  • Hap_Hazzard
    Hap_Hazzard Member Posts: 2,849
    One more thing

    Which way does this thing drain? If this is a concurrent flow system, that reducing tee has to go. You need to either replace it with an eccentric version of the same fitting or else run 2" pipe all the way to the return. Eccentric fittings are hard to find, and you might need to use multiple fittings to make this transition.
    Just another DIYer | King of Prussia, PA
    1983(?) Peerless G-561-W-S | 3" drop header, CG400-1090, VXT-24
  • 4Barrel
    4Barrel Member Posts: 125
    where the water collects

    very helpful posts. yes, that reducing T is where the water

    collects. need to fix the real problem here.

    this is concurrent flow for the main.  the whole section (including

    reducing t and short 1-1/2" length) is about 14', 8' of it is unsupported. this

    is what you see in the accompanying pic. the main is pitched to the final

    elbow, BUT the small run outs are pitched back to the main, contributing to the


    I had considered cutting the section about 4' back from the reducing T. see

    close up pic of pipe condition. it's rusty and pitted on the surface, but seems

    solid. however, I uncovered the next closest fitting (see pic) and contrary to

    my earlier post, I think have enough room work should I choose to remove the

    whole section.

    I like the idea of running 2" pipe to the end. I’m thinking I need to add

    a drip at the end though, to give condensate from the counter-flow run outs and

    any leftover from the main someplace to go. perhaps replace the final elbow

    with a T with an eccentric reducing fitting and then drop and connect in to the

    dry return? open to ideas on how to re-pipe this sucker so I don’t have to

    revisit this issue.
  • 4Barrel
    4Barrel Member Posts: 125
    downsize main?

    i've decided to replace the entire 14' section, and i've got a plan to pipe in a end of main drip and return, which will address the water collection issue.

    but i'm thinking that i do not need to replace that length of main with 2" pipe. this section  serves the last two radiators, representing 18% of the connected load for this main.

    can i use 1-1/2 for this final run instead? it's simplier... and of course less expensive for the fittings.
  • 4Barrel
    4Barrel Member Posts: 125
    Repair Complete

    got the new section piped in. as of this pic, still have a couple hangars to add and insulation... so far all the joints are tight.

    couldn't resist slicing a couple sections of the old pipe... the wall along the bottom had deteriorated to less than half the width, and had blown right through in a few spots where the water had pooled.... sure am glad i replaced the whole section.

    thanks to for the advice.
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