Underground PVC pipes can sustain damage due to encroaching tree or plant roots, or from animals digging underground. Repairing an underground PVC pipe will require some effort on your part to dig up the broken pipe. Locating the leak can also present a challenge. Once you've identified the leak, you can easily make the repairs at very little cost and complete them within about 6 hours, after the sealants have all set.
Locate the leak; you'll spot it easily if you have a flooded area in your yard. In addition, if the PVC pipe connects to a sprinkler system, the damaged line will simply not operate the sprinklers attached to that line.
Turn off the water main. You may need to contact the city to have your water shut off if your home runs off of city water, or you may have access to shut off the water main directly at your home.
Dig along the side and top of the PVC pipe. Locate the leak, and expose the surrounding area alongside that pipe to evaluate it for further damage.
Evaluate whether you will need to replace the entire PVC line, or just that section of piping. If you have a long section of pipe that appears intact, replacing the entire line may not be cost efficient.
Cut out a section of pipe by sawing through the pipe 6 inches outward from each side of the damaged area. This will ensure you also cut out any hairline fractures or other damaged parts in that area.
Evaluate the surrounding area of soil for what may have caused the damage to the pipe. If a tree or plant root seems to be the culprit, cut the root entirely around the piping—it should extend to no more than 4 feet from the piping. If possible, transplant the tree or plant to avoid future problems along the same PVC line.
Cut a new portion of PVC pipe to put in the remaining gap on the line. Make sure it will fit snugly and securely without any gaps.
Apply the silicon sealant along the ends of each side of the new PVC pipe part. Place the new section in place along the line, securing it in place. Hold it for several minutes to ensure it will not slip.
Install the coupling joints over each of the sealant lines. Tighten them securely in place, and let them set for at least 2 hours.
Turn the water main back on and test the line to ensure the sealant has set and that no other leaks have developed along the line. Let the system run for at least 20 minutes.
Once you have tested the new line and determined that it runs smoothly, place the surrounding dirt back around the PVC pipe and cover it up completely as before.