Capp off galvanized water line under slab

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by Backwoods, Jan 26, 2012.

  1. Backwoods

    Backwoods New Member

    Messages:
    8
    Location:
    Lebanon, MO
    I'm demoing a bathroom and converting to a hallway. The sink was right in the middle of my new doorway on a load bearing wall. The supply line, 1/2" galvanized pipe ran into wall and down into slab. I have chipped away at concrete down about 2" and want to jackhammer back to the main line but it's running under the wall about 3' to main supply. I need to keep water flowing to another bathroom beyond this one. My question is, is there a compression fitting I can use that would be dependable or do I need to thread the pipe where I cut it below concrete? I've heard compression fittings are not recommended for galvanized pipe. Any help would be appreciated as I need to move on with the project. Thanks
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,023
    Location:
    New England
    Can you get down to the T, unscrew the stub, and then put in a plug?

    Galvanized is a time bomb...underneath a slab is a worry.
  3. Backwoods

    Backwoods New Member

    Messages:
    8
    Location:
    Lebanon, MO
    Capping off galvanized water line under slab

    I posted last night but it is gone this morning, maybe a dumb question, I dunno. Anywhow, I've demoed a 1/2 bath to make a hallway thru it. The sink was in the middle of new doorway to hall. The galv pipe ran from sink into bearing wall and down into slab. My question is there a compression fitting anyone would recomend or does it need to be threaded? The pipe runs under the wall for approx 3' to another supply line to where the toilet was. I need to leave the water flowing to another bathroom beyond. Any help will be appreciated. I'm a carpenter and new to the area I'm in. No plumber can be available until Monday and I need this done now. I can do it just, don't have experience with galv. pipe and being under slab I need to get it right.
  4. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,647
    Location:
    Cave Creek, Arizona
    There has to be a fitting where it turns and goes horizontal under the wall. Remove the pipe from that fitting and install a plug in it. Every threading option will take a much larger hole than you have, or want to make.
  5. Backwoods

    Backwoods New Member

    Messages:
    8
    Location:
    Lebanon, MO
    Thanks alot. I'm going to get jackhammer after lunch. I think I'll try to get down to the elbow where it goes horizontal and plug it. I guess I was hopin for easy fix and shoulda known better. I appreciate the feedback and will let ya know how it went.
  6. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,647
    Location:
    Cave Creek, Arizona
    IF you were trying to seal the pipe without breaking the concrete, HOW did you expect to do it below the floor? If it is a bearing wall, the pipe will be in a "grade beam" under the concrete, so you may need more than a "little jack hammer".
  7. Backwoods

    Backwoods New Member

    Messages:
    8
    Location:
    Lebanon, MO
    I knew I was going to have to get into the slab. I used a small chipping hammer and am down 2 to 3 inches. Was thinking maybe a compression fitting would be sufficient. I'm not sure if it is all in the footer. Surely they didn't pour water line length of the grade beam thats another reason I was hesitant about jack hammering because not sure how deep it is. It's a very old building, but the pipe seems to be in relatively good shape. I have a 90# jackhammer and will get on it first thing in the morning. After reading on here and other discussions a compression fitting doesn't seem to be a option and I don't have a threading tool but can probably rent one if I have to. Thanks for the response and ideas
    Last edited by a moderator: Jan 27, 2012
  8. Hackney plumbing

    Hackney plumbing Homeowner

    Messages:
    1,174
    Location:
    Alabama
    Alot of people dont know it but a 3/4 sharkbite cap will slip over and seal around a 1/2" galvy pipe in new condition. I did it for kicks and hydrotested it to over 200lbs for a few days.......then i dropepd the pressure to 90 psi and left it for 6 months. Thats with no vibration,no flow,etc.....it was on a test bench.
  9. rap

    rap New Member

    Messages:
    63
    Location:
    california
    Just saying, without knowing the lay-out, but can you see your way to abandoning the in-place galv. and picking up your supply (s) beyond any heroic jack-hammering, and then snaking through say, plastic pipe. Even though there will be further disturbance, perhaps if you do now what will have to be done eventually ie. replacing the galv. then you will be ahead of the game.
    Dont, of course, cut off the galv. until you have everything new, tested and in position.
    What do i know, anyway it's just a thought.
  10. Backwoods

    Backwoods New Member

    Messages:
    8
    Location:
    Lebanon, MO
    Replacing the galv. is not a option right now. I have used the sharkbite before on old quest and above ground, they work great. But I'll be hammerin tomarrow. I'll feel alot better getting it capped at a threaded joint. Any specific dope for the threads??
  11. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,023
    Location:
    New England
    Assuming the threads are intact when you unscrew the pipe, any pipe dope, applied properly, and the plug well seated should seal the now unused port.
  12. Backwoods

    Backwoods New Member

    Messages:
    8
    Location:
    Lebanon, MO
    Thanks alot everyone. I'll post some pics when finished
  13. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,647
    Location:
    Cave Creek, Arizona
    quote; I'll post some pics when finished

    IF you have seen one cap or plug, you have seen them all.
  14. MACPLUMB 777

    MACPLUMB 777 TROJAN WORLDWIDE SALES RP

    Messages:
    679
    Location:
    Houston, Texas, United States
    I would leave open a day or two to confirm that there are no leaks !

    Or at least overnight

    plumbers know that when you mess with old glavy, especially under ground any vibration can do unexpected things maybe down the line somewhere from your hole may take a little while to show up
  15. Backwoods

    Backwoods New Member

    Messages:
    8
    Location:
    Lebanon, MO
    Gotter done today. actually yesterday since its 1:25 AM here in Show-Me State. Jacked it out with no problems. The elbow was only 5" down, right at bottom of concrete. Wasn't in the grade beam at all. 18" pipe wrench and a 24" breaker bar and a 1X4 backer to keep the whole thing from twisting it came off fairly easy. It's capped and water back on with no leaks. Would ya'll suggest wrapping it before I pour it back tomarrow, assuming it's not leaking when I go back in the morning. What do I wrap it with? You know, I'm just a 'ol worn out carpenter who has to "gett er done" and would of hired a plumber in a heartbeat to do this but short notice and on a weekend couldn't find one to do it, and I can understand why now, it wasn't that bigga deal. But hey, it's old galvanized pipe under a slab, I didn't have any idea what I was up against. So I'm glad I found this forum for some advise. Thanks all! And hj I won't post a pic, 'cause your right, it won't impress anyone.
  16. Backwoods

    Backwoods New Member

    Messages:
    8
    Location:
    Lebanon, MO
    MACPLUMB 777. I will wait at least 24 HRS. before I put the crete to it. thanks
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