How to Fix Water Lines Under a Slab House

Determine the source of the leak. Finding the leak can be a problem if the damaged water line is located deep within the house structure. You may be able to detect the leak by pressure differences in faucets. A leak in a hot water line can often be detected by warmth on the floor where the leak has occurred.

Turn off the water at the main house valve.

Remove all floor coverings from the work area, as well as subfloor boards until the concrete slab is exposed.

Cut a hole in the foundation slab using a jackhammer large enough to expose the damaged area of pipe and to allow work on it. Most house slabs are 3 to 5 inches thick, so considerable work is required to break through this thickness.

Remove the damaged portion of pipe by unfastening it at nearby connections or by cutting it if necessary.

Replace with a new section of pipe of the correct length. The pipe should match the existing pipe -- that is, copper to match other copper pipe, gray poly for gray poly pipe or PVC for PVC pipe. Connect into place using a suitable connector, wrapping the threads with plumbers tape for a leak-proof fit. Tighten the new pipe securely.

Turn the water to the house back on. Ensure that there is no leak from the new section of piping that was installed.

Mix concrete and re-patch the open area. Smooth the wet concrete to an even surface with a trowel and allow to dry thoroughly according to label directions.

Replace flooring materials over the repaired area.