Under the sink in the restroom, there is a slight water leakage at the connection between the shut-off valve and the water pipe (picture).How can I resolve this?

My current budget is limited (~$500), and I plan to wait several years before a complete remodel. Therefore, I'm looking for a solution that can last for several years. I'm no stranger to DIY projects and I'm open to acquiring new skills.

Thank you in advance!

Picture Link


  • The water pipe appears to be made of iron and can be attracted by a magnet.
  • The house disclosure says the water supply lines are made of copper without any other details.
  • The other shutoff-value connection on the left seems okay now.
  • The rate of water leakage is currently acceptable; it leaks about half a basin per week. However, I am concerned that the rate may increase, making me have to shut off the main valve.

the leaking valve

the connection

the connection 2

1 Answer 1

  1. Turn off the whole-house shutoff valve.
  2. Drain the supply piping enough so you can remove the leaking valve without creating a gushing flood. Opening a few valves at a lower level should do the trick.
  3. Unscrew the offending valve. Use two wrenches: a pipe wrench to hold the steel pipe stationary, and an adjustable open-end wrench on the flats of the valve. Inspect it carefully for splits or damage at the threaded end. Have a new valve on hand in case it's damaged and needs replacement. Also have on hand a new threaded pipe nipple to replace the one in the wall. It's obviously been leaking for a long time and may be rusted/corroded beyond further use. Be aware that attempting to repair old steel pipe can lead to a never-ending chain of disasters.
  4. Clean up the threads on the steel pipe as well as you can with a wire brush.
  5. Apply liberally a thread-sealing paste to the threads of the pipe.
  6. Screw the valve back on, again using two wrenches.
  7. Make sure the valve is turned off, turn the house main valve back on, check for leaks.
  • Just a note to OP that getting the old valve off the galvanized pipe is, in many cases, 80% of the battle.
    – SteveSh
    Dec 29, 2023 at 12:42
  • Thank you so much for the detailed instructions! I will give it a try.
    – ydix
    Dec 31, 2023 at 18:49

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