Learn how to make damaged copper pipes look and work like new again.

October 23, 2017

Because of its durability, copper is the preferred material for most water supply lines. However, copper pipe can leak when dented, punctured, or weakened from corrosion. Joints can degrade too. Luckily, this section will walk you through basic copper pipe repair.

Before you begin, there are a few things to keep in mind. For example, even if you have galvanized or plastic supply pipe in your house, you may want to use a transition fitting and switch to copper when making a repair or extending a line. When joining copper pipe to steel pipe, be sure to use a dielectric fitting to avoid corrosion.

Type M copper pipe is fine for most residential work, but make sure to buy lead-free solder and flux paste. Also recognize that sweating a large copper drain line calls for a large propane torch; you're probably better off hiring a pro for such work. Compression fittings, on the other hand, require no special skills to install, but they are expensive. Use them only where they will be exposed; any joints hidden in a wall must be sweated.

Expect to spend about an hour or two for most repairs. Before you begin, shut off the water; drain the line; and position a cookie sheet or protective shield to protect flammable surfaces.

What You Need

  • Groove-joint pliers
  • Tubing cutter
  • Hacksaw
  • Multi-use wire brush
  • Flux brush
  • Propane torch
  • Fiber shield
  • Copper pipe and fittings
  • Flux
  • Solder

Step 1: Shut Off Water and Cut Pipe

Shut off the water. Use a tubing cutter to cut on each side of the damaged area. Screw the cutter tight, rotate it a full turn, tighten, and rotate again until the cut is complete. If there is not enough room, cut with a hacksaw. Exert gentle pressure to avoid flattening the pipe. File off burrs.

Step 2: Cut New Piece

If either of the existing pipes is movable, you can use standard couplings. If not, use slip couplings. Measure the replacement piece by holding it in place. It should be the same length. Cut the new piece with a tubing cutter.

Step 3: Install Couplings and Replacement Piece

Ream and polish the pipe and couplings using a multiuse brush. Brush on flux and slide a coupling on each side, position the replacement piece, and slide the couplings back halfway. (To install a standard coupling or elbow, give it a slight twist as you push it all the way into place.)

Step 4: Flame Fitting

Protect framing and nearby walls with a cookie sheet or fiber shield. Aim the torch so the tip of the blue flame touches the middle of the fitting. When the flux sizzles after 5 seconds or so, move the flame to the opposite side and heat it briefly. Touch solder to the joints.

Step 5: Wipe Joint

Once solder has been sucked into the joint all around, wipe the joint with a rag to smooth the solder and eliminate any drips. Fold the rag several times and/or wear leather gloves. Repeat for the other side of the fitting. Check the work area an hour later to be sure nothing is smoldering.

How to Add a Copper Supply System

Rigid copper joints are soldered together. The resulting joints, if made correctly, are at least as strong as the pipe itself. To add a supply line, install a tee fitting. Use a compression fitting only if it will remain exposed for inspection.

How to Install Compression Fittings

Compression fittings often make sense in tight places where it is difficult to solder. To install one, slide the nut, then the ferrule, onto the pipe. Slip the fitting onto the pipe, slide the ferrule into the fitting, and tighten the nut. No thread tape or pipe compound is necessary.

How to Patch a Pipe with a Tape Kit

While not as fail-safe as a sweated patch, fiberglass patch tape can provide a quick, long-lasting cure for a leaky pipe. The kit includes tape impregnated with resin, gloves, and a lubricant that helps you squeeze out voids and bubbles.


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