Fixing a leaky copper pipe with putty stops the seepage until a plumber can permanently repair the leaking section of pipe. An epoxy-based putty bonds with the copper pipe's surface and forms a watertight seal. Pressing the putty into the copper pipe's leak increases the strength of the patch. Once the putty cures, it hardens into a solid patch that cannot peel off the copper pipe's surface. The putty hardens to a point where a plumber must cut out the fixed section of copper pipe before repairing the pipe permanently.
Turn off the water supply to the leaking copper pipe. Turning the water shut-off valve's handle counterclockwise closes the valve.
Open a sink faucet or hose bib to drain the water from the leaking copper pipe.
Clean a 1-inch section of the copper pipe on both sides of the water leak with either sandpaper or a wire brush. Remove all corrosion from the pipe's surface. Extend the cleaned area around the perimeter of the pipe.
Cut a 2-inch-long section of putty from its roll, using a knife.
Knead the putty with your fingers until its inner core blends with its outer core. The two parts of the putty have different colours. Blending the putty fully gives the putty a uniform colour. The two parts of the putty react with each other.
Press a small amount of the blended putty into the leak's hole.
Wrap the remaining putty around the cleaned area of the copper pipe, forming at least a 1/8-inch-thick, 1-inch-wide layer of putty all the way around the pipe. Press the putty against the copper pipe's surface and into the putty you pressed into the leak in Step 6.
Wait the putty manufacturer's recommended cure time, usually 15 minutes, before turning on the water.