How to Repair Plumbing Leaks Under Concrete Slabs

Locate the precise area of the leak. This investigation can be difficult because moisture can develop at various points along plumbing junctures. You may wish to consult with a plumbing contractor who has special electronic equipment that can help you to determine the source of the leak.

Remove the carpeting or other floor surface over the leak area.

Open up an area in the concrete slab above the leaking pipe using a jackhammer or similar concrete-cutting equipment. This equipment is available at rental outlets. The concrete can be broken in several sections for easy removal.

Turn off the water to the house at the main water shutoff valve. Open a faucet in the home to allow the water to drain out of the lines before cutting into the pipe.

Cut out the bad section of pipe with a hacksaw.

Measure and cut a new section of pipe with a hacksaw to replace the damaged section.

Attach the new section of pipe with a fitting. For copper pipes, "sweat" the new pipe and fitting into place by heating with a propane torch and gradually adding solder to seal the joint. For PVC pipe, apply plastic pipe adhesive to seal the joint, which melts the pipe materials together. Cast iron pipes must be cut and threaded, and then attached to fittings. The threaded end should be wrapped with plumbing tape to seal the joint.

Fill in the dirt around and on top of the repaired pipe.

Remove all concrete pieces, dirt, mud and other debris from the repair area.

Mix the concrete according to package directions.

Apply the new concrete mixture to fill in the removed area, and smooth to a level and even surface with a trowel.

Allow the concrete to dry thoroughly for several days. Keep foot traffic off the area while the concrete dries.

Repair or replace the flooring over the leak area.