Things You'll Need
2 coupler fittings
Copper is one of the main types of pipe used in home water lines. Over time, the pipes may develop leaks around the connections, or pin holes may form in the pipe's walls, leading to larger leaks. The most effective way to repair copper pipe is to remove the bad section and replace it with a new piece, joined with copper fittings.
Trace the water to where it is seeping out of the pipe.
Turn off the flow of water to the pipe at the closest main shutoff valve.
Cut out the leaking section of pipe, using the the pipe-cutting tool. Cut the pipe a few inches away from the leak on each side of the leak. Discard the bad section of pipe. Sand the two ends of the pipe with the emery cloth until they are shiny. Dry the two ends of the pipe with the cloth.
Dry-fit the couplers by sliding them on each end of the cut pipe. Measure from the middle ridge of each coupler with a measuring tape to determine the length to cut the replacement piece of copper pipe. Once you have the measurement, remove the coupler fittings.
Cut the replacement piece of copper pipe from the new section, using the measurement. Sand the ends of the pipe with the emery paper until shiny.
Brush one end of the replacement pipe with flux so that about 1 inch is covered with a thin coating. Slide one end of one of the coupler fittings onto the fluxed end of the pipe. Use the torch to heat the area where the pipe and coupler are joined until you see the flux begin run and drip off. Apply solder to the joint on the opposite side and work your way around the connection. Allow the heated pipe to draw the solder into the connection, sealing it up. Repeat this step to attach the remaining coupler to the other end of the replacement copper pipe.
Apply flux to one end of the existing copper pipe. Slide one end of the replacement pipe, with its coupler, over this fluxed end of pipe. Solder the fitting and pipe together with the torch and solder.
Apply a thin layer of flux to the end of the remaining copper pipe.
Pull the remaining end of the existing copper pipe gently in any direction it will go until you can slide the coupler over the end of the existing pipe. Solder this connection together.
Turn the shutoff valve back on and test for leaks.
Use caution when operating the torch, and do not operate it around any combustible or flammable materials that may lead to a fire or explosion from the open flame.