Corroded threading help

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by pocoloco, Aug 8, 2009.

  1. pocoloco

    pocoloco New Member

    Messages:
    23
    Location:
    Illinois
    The threading on my cold supply line (galvanized) under the sink has partially corroded away. I can still screw on the shutoff valve but it leaks. How do I fix this? Thanks in advance.
  2. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,525
    Location:
    Cave Creek, Arizona
    pipe

    Replace it with a brass nipple.
  3. pocoloco

    pocoloco New Member

    Messages:
    23
    Location:
    Illinois
    So are you saying replace the entire pipe coming out of the wall with a brass nipple? Would I need to open the walls up, or would I just unscrew the existing pipe that's coming out of the wall and then stick the brass nipple into the wall and screw it on? Sorry if I'm being so elementary... I consider myself handy but plumbing is obviously not my forte. Thanks
  4. seaofnames

    seaofnames DIY Senior Member

    Messages:
    162
    Location:
    Mission, BC
    Repipe.

    It may last another 10 years, but its gonna have to be done eventually once it fails like that.
  5. pocoloco

    pocoloco New Member

    Messages:
    23
    Location:
    Illinois
    When you say repipe, do you mean replace all the pipes in the walls? From where to where? Are you suggesting an entire house replumb?
  6. TedL

    TedL New Member

    Messages:
    604
    Location:
    NY Capital District
    The long term solution is to get rid of all the galvanized, as suggested above.

    The short term solution is to replace the one defective part, the nipple. At this point, upgrading the replacement to brass seems a waste, but perhaps there's a reason for it.

    You should not need to open the wall to do it. If the wall is caulked or plastered to the pipe, merely remove 1/8" or less of the material. Use tape and dope on the new nipple to ensure no leak in the hidden location.
  7. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,525
    Location:
    Cave Creek, Arizona
    pipe

    The pipe should unscrew from the fitting in the wall, and then you can screw the new one into it.
  8. pocoloco

    pocoloco New Member

    Messages:
    23
    Location:
    Illinois
    Thanks everyone for putting up with my novice questions. It's all very clear now.

    I will unscrew the old pipe from the fitting in the wall and screw on a new nipple with tape + dope (Rectorseal 5 pipe sealant is what I have).

    Just a few more stupid questions...

    1. Do I put tape on first, then the dope?
    2. What type of wrench/tool should I use to screw on the nipple?
    3. I'm nervous that it will now leak in the wall. Am I being paranoid or should I rest assured it will be fine given I follow the steps above?

    Thank you!
  9. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,934
    Location:
    New England
    This is what a pipe wrench is designed to do. You may get it loose with some big pliers. If there's not enough sticking out to grab with a wrench on the outside, they do make an internal pipe wrench - it has a cam on it that tightens against the inside as you use a wrench on the shaft.

    Yes, it could break off inside. Probably won't, but you never know.

    Tape, then dope, if you're using both.
  10. TedL

    TedL New Member

    Messages:
    604
    Location:
    NY Capital District
    If you don't have a pipe wrench, a vise grip may work if it will give you enough leverage.

    Since it's inside a sink base or behind an escutcheon plate (or both), you can cut away 1/4" to 1/2" of the wall at the bottom of the nipple, and after a day inspect with a flashlight or probe with a Q-tip for water drops where the nipple meets the elbow inside the wall. You should then be able to sleep easy. ;)
  11. pocoloco

    pocoloco New Member

    Messages:
    23
    Location:
    Illinois
    Excellent, you guys rock! thanks for all the help.
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