Nicked a 3" pipe with my saw

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by dgreen1069, Feb 20, 2007.

  1. dgreen1069

    dgreen1069 New Member

    Messages:
    17
    Location:
    Northern VA.
    While moving my shower drain a few inches I accidently cut the 3" PVC pipe that was directly below it. The cut is about 1" long, the width of a reciprocating saw blade (about 1/16th") and is directly on top of the pipe. I was planning on priming the cut and applying cement to seal it up. I will also cut one of those 3" rubber connectors and place it over the cut with clamps and cement (just for good measure).

    Is this a legitimate fix for what seems to be a minor problem, or do I need to cut out the cut area and add a splice (very tough since under slab)?
  2. Cass

    Cass Plumber

    Messages:
    5,980
    Location:
    Ohio
    If it didn't cut through the pipe you should be fine. You could fill it with epoxy.
  3. leejosepho

    leejosepho DIY scratch-pad engineer

    You dare not expose the PVC to any actual flame lest it quickly overheat and either burn or shrink away while trying to kill you with its smoke, but you can actually weld PVC with hot air, and/or you can use a hot (but never red-hot) tool or heavy blade of some kind to "smoosh it around" a bit. And, that is what I would likely do in a case such as yours.

    Do a web search for "pvc welding" or "plastic welding" and read a little and you can learn more about all of that. If you know about brazing or gas welding, the principle is essentially the same: heat and filler rod. And if you check with a local auto parts store or two, you are likely to find a relatively inexpensive kit for welding PVC/plastic quite effectively and safely.
  4. TedL

    TedL New Member

    Messages:
    604
    Location:
    NY Capital District
    Instead of rubber, I'd cut about a 1/2 (180 degree) arc out of a 3" PVC hub and solvent weld it over the cut.
  5. Cass

    Cass Plumber

    Messages:
    5,980
    Location:
    Ohio
    If your going to go to all that, cut it in 2 places and reattach it using 2 non banded rubber couplings.
  6. TedL

    TedL New Member

    Messages:
    604
    Location:
    NY Capital District
    Don't know if that's a reference to my suggestion, but if it is, "all that" would be about 40 seconds to make 2 cuts on a chop saw, and another minute to apply the solvent and hold it while it sets.
  7. dgreen1069

    dgreen1069 New Member

    Messages:
    17
    Location:
    Northern VA.
    OK, I think I may have taken the wrong approach trying to do the easy fix. The cut does go into the pipe (I can slip a saw blade into the cut). I'm thinking now the only way to fix it properly is to cut the pipe and put in a joint of some sort. Are the flexible black rubber couplings with hose clamps code compliant? I am getting the drain I moved inspected tomorrow and don't want to fail because of the nicked pipe. I'm sure I could hide it, but I want it permenantly and correctly fixed (it will be under concrete).

    Since the pipe is under my slab there isn't a lot of wiggle room to move the pipe any direction. I have adequate space in the hole I created to work, but I don't know if I can get a solid coupling in place. What would you guys do? If I cut the pipe and take out an inch or so, can I use one of the black rubber couplings with the metal sleeve and hose clamps? What is the most correct product that will be a one time fix and code compliant? Keep in mind that I am working under my slab.
  8. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,932
    Location:
    New England
    Underground, the rubber sleeve is code, above ground, you need a banded coupling - similar, but is metal reinforced with a band.
  9. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,522
    Location:
    Cave Creek, Arizona
    nick

    the easiest permanent repair is to do as suggested previously. Take a repair coupling without a center bead, or grind the bead out of a regular one. Cut the coupling longitudinally slightly past the center line, about 190 degrees, coat the pipe and coupling with cement and "snap" the coupling over the cut. It will never fail, not leak.
  10. leejosepho

    leejosepho DIY scratch-pad engineer

    Yep. I thought about that myself just a little while ago. Your cut will be completely covered and sealed, and the pipe will be even stronger than it was before the incident. Clean the parts as usual, apply the cement to both, snap the repair piece over the pipe and put a little pressue on it for a few seconds ... then step back and know you have done well!
  11. dgreen1069

    dgreen1069 New Member

    Messages:
    17
    Location:
    Northern VA.
    I will purchase a slip coupling tomorrow and do as you guys say....I'll cut it in half and glue it over the cut. Thanks for the advice.
  12. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,522
    Location:
    Cave Creek, Arizona
    coupling

    A little more than half so it snaps on, and doesn't just sit over the cut.
  13. dgreen1069

    dgreen1069 New Member

    Messages:
    17
    Location:
    Northern VA.
    I figured I'd also get a Fernco coupling and slice it down the center to put over the hard patch. All that and 80 lbs. of concrete should do the trick. Odds are water will never get to the top of that pipe anyway....it should be draining right out.
  14. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

    Messages:
    2,714
    Location:
    Central Florida
    Hey, don't go nuts. After all, it's only under about 0 psi.
  15. prashster

    prashster New Member

    Messages:
    941
    I drilled a hole in a drain pipe a couple weeks ago. Epoxy worked for me. I didn't have enough room for the 'snap' coupling HJ and TedL describe since the pipe was too close to each wall.


    I also practiced the hotmelt method with a propane torch and a metal putty knife. Only ended up burning my practice pipe and not covering the hole at all. Opted for epoxy. But that's just me.
    Last edited: Feb 21, 2007
  16. dgreen1069

    dgreen1069 New Member

    Messages:
    17
    Location:
    Northern VA.
    I had plenty of room to work on the pipe, just no room to put in a slip joint without having to cut the pipe two places. I used HJ's method and cut a slip joint to make a 190 degree C. I sanded down the cut where I had previously put on PVC glue and I reprimed everything. I applied PVC glue to the pipe and C fitting and slapped it all together. I don't see how that is much different than glueing any other two pieces of PVC together. Hopefully it is a strong weld. For good measure I put a Fernco coupling over the patch to keep everything in place. I'm sure it will be fine. My only concern was being under my slab....I'll never see that pipe again. I needed a one time fix that I didn't have to worry about. Thanks for all the replies.

    As others have said, the pipe is under 0 pressure. There should never be standing water in the pipe so freezing shouldn't be an issue either. Hopefully it will never be an issue. Under my concrete slab I'll probably never know.
    Last edited: Feb 21, 2007
  17. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,522
    Location:
    Cave Creek, Arizona
    cut

    The Fernco does absolutely nothing for the repair, once is is cut apart. The clamps can only "seal" the ends, so once it is slit longitudinally, there is no way to clamp the center sections against the pipe. But since the PVC coupling is actually doing the sealing, anything else is just to make you feel good.
  18. dgreen1069

    dgreen1069 New Member

    Messages:
    17
    Location:
    Northern VA.
    I already had the Fernco from my friends first repair :) I figured since I had it, I would use it to make double sure the PVC coupling stayed put after it had been cemented.
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