How to Fix a Leaky Copper Pipe Under Concrete

Search the area to approximate where the leak is coming from. Look for excessive moisture, mold growth or excessive moisture.

Turn off the main water valve to prevent the pipe from getting more water as you work on the repair. Open a faucet nearby to give water already in the system a place to escape.

Drill through the concrete with a jackhammer or drill to work your way down to the pipe. Be careful to not break through the pipe as you jackhammer, because the pipe is likely only a few inches underneath the surface.

Cut the leaking portion of pipe out with a pipe cutter. Use the broken piece to cut a replacement piece of copper piping, called a "sweat coupling," that's about an inch longer than the original.

Clean the old pipe and the new one by running a pipe brush through them, and then by scrubbing them vigorously with fine sandpaper. Wipe the pipes with a rag to remove any loose sand.

Slide the replacement copper pipe over one section of the old pipe, and then fit it into the other section.

Solder the replacement pipe at both joints by holding a solder wire on one side of the pipe, while running a soldering torch over the other. This melts the solder so it flows around the pipe and hardens. Keep the pipe as dry as possible for best results during the process.

Fill the hole in the concrete with concrete mixture from a bag. Mix the concrete with water in accordance with package instructions. Even it out with a trowel after pouring it, and allow it to dry. It dries in several hours, but it takes over a week to solidify fully as it reacts to the air.