The focal point of your backyard has sprang a leak, and instead of a pond you find yourself with a half-empty puddle. Fortunately, modern pond liners are made of PVC and it's likely you'll never encounter this scenario. But if you do, try finding and fixing the leak yourself before calling in the local pond expert. The good news is that most leaks are easy to repair. Finding the leak may be a tougher task, but there are a few methods to try.
Remove any plants or fish and store them safely elsewhere. Remove rocks or any other materials that cover the liner and may obstruct a search for the leak.
If your pond is losing water rapidly but you cannot locate the leak, slowly pour milk or lightweight sand into the pond and watch for the leak to draw it through the water.
If the leak doesn't pull the sand or milk toward it, turn off the pond pump. The water will stop draining when it reaches the level of the leak.
If the pond drains completely and you cannot find a leak, use a wet/dry vacuum to remove all water and organic material. Rinse, and vacuum again. Let the pond liner dry completely.
When the liner is completely dry, run a garden hose beneath the liner. Run the water until it comes up through the hole in the liner.
Scrub the area for several inches around the leak with a bristle brush, removing all non-liner material. Allow the liner to dry completely.
Determine what kind of leak you have -- whether it's a puncture, worn or deteriorated liner material, or a rip or tear.
If you have a puncture, or the liner is worn around the hole, trim any distorted or deteriorated material until you have a smooth, strong surface with which to work. Cut the patch material slightly bigger than the hole.
Apply the sheeting cement and allow it to dry per the directions on the container.
Apply the patch, pressing firmly with your hands or with the paint roller to avoid creases or wrinkles. Allow the repair to dry per the cement directions, and then refill your pond.
If you buy your repair materials as a kit, follow the instructions included with it. PVC sheeting cement is available at plumbing or home improvement supply stores. It is a contact cement used for securing white shower stalls.
Don't lift the liner up from the ground, or you risk the dirt beneath it moving, which will reshape your pond. Do not use PVC pipe cement.