How to Fix a Leaky Pipe Joint

Dry the pipe thoroughly and identify what kind of joint you're dealing with. Compression fittings have a visible nut and ferrule (sleeve) where the pipe enters the fitting. Threaded joints show visible pipe threads. Soldered copper joints appear as a smooth, silver ring where two copper pieces meet. Run water and use a paper towel to pinpoint the exact drip location.

Close the nearest shut-off valve upstream of the leak. If there's no local valve, shut off the main water supply to the house. Open a faucet downstream of the leak to relieve pressure and drain residual water. Place a bucket under the joint to catch any drips during the repair.

Compression fittings are the most common under-sink joint. First, try tightening the compression nut a quarter turn clockwise with an adjustable wrench. Run water and check. If it still leaks, shut off water, unscrew the nut, slide it back, and inspect the brass ferrule (ring) for damage or misalignment. If the ferrule is scored or cracked, slide it off and replace it with a new one of the same size. Re-seat the pipe into the fitting, slide the ferrule and nut back, and tighten snugly.

For a leaky threaded joint, unscrew the fitting (turn counterclockwise). Clean the male threads with a wire brush to remove old tape or compound. Wrap new Teflon tape clockwise around the threads — three to five wraps, keeping the tape tight and smooth. Apply a thin layer of pipe joint compound over the tape for a belt-and-suspenders seal. Screw the fitting back on hand-tight, then add one to one-and-a-half turns with a wrench.

Soldered joints require more skill. Drain the pipe completely — even a small amount of water prevents solder from bonding. Heat the joint with a propane torch until the old solder melts, then pull the pipes apart with pliers. Clean both surfaces with emery cloth until they're shiny. Apply flux to both the pipe exterior and fitting interior. Reassemble, heat the joint evenly with the torch, and touch lead-free solder to the joint — it will wick into the gap by capillary action. Let it cool undisturbed for two minutes.

If you need a temporary fix until you can do a proper repair, dry the leaky area thoroughly and wrap it tightly with self-fusing silicone repair tape, overlapping each wrap by half. This tape bonds to itself and creates a waterproof seal that can hold for weeks or months. Alternatively, apply a pipe repair clamp (a stainless steel sleeve that bolts around the pipe over a rubber gasket).

Turn the water back on slowly and observe the repaired joint for a full five minutes. Wipe the joint completely dry, then wrap it with a paper towel and leave it for 30 minutes. Check the paper towel for any dampness. A properly repaired joint should be completely dry. Check again 24 hours later to catch any very slow seepage you might have missed initially.