Turn off the water supply to the area of the copper pipe being resoldered. Locate a shut-off valve close to the area or shut off the main water valve to discontinue the water supply to the entire house.
Dry the area of the pipe where the leak is located using rags to wipe off the moisture. Allow the pipe to stop dripping and dry completely before attempting the repair.
Soak the rags with cold water and place them in the work area.
Sand off as much of the old solder as you can using a medium-grit sandpaper. Sand around the entire circumference off the pipe. You will not remove all the old solder, but the more you can remove the better chance the new solder will have to bond.
Ignite a propane torch and unwind about 6 or 7 inches of the silver solder. Hold the tip of the flame from the propane torch on the connection being repaired. Move the flame over the entire area for a minute or two to heat the connection thoroughly.
Touch the tip of the solder to the pipe connection and move it around the entire circumference of the pipe. Ensure that the solder covers the entire connection. Place a cool damp rag over the solder to cool it quickly so it bonds to the copper better. Allow the solder to fully cool for 10 minutes before turning on the water supply.