PVC, or plastic water pipe, is very common in most newer homes. This type of pipe is designed to last a very long time, but occasionally it can develop leaks or cracks, depending upon the chemicals in your water, or whether you have used any drain cleaning chemicals in your drain pipes. If you have developed a small leak in a pipe elbow, you can repair it without having to take the entire joint apart.
Drain the water from the system that travels through the pipe in question. You may have to turn off the water to your entire house, or you may only have to turn off a local valve, depending on the location of the leak. The pipe will need to be dry for repair.
Clean the small leak with PVC primer. This cleans the surface and allows the PVC cement to stick well.
Fill the leak with PVC cement and allow the cement to dry. This will melt the leak together, and it will seal itself.
Apply plastic epoxy over the repair to ensure that it will hold for a long time in the future. Allow the repair to dry according to the time specified on the epoxy tube.
Test the repair for leaks. Once the repair is complete, turn the water back on and make sure that the elbow is not leaking any water. If you do find a new leak, repeat the process or cut off and replace the entire joint if the leak is too large.