If you believe you have a leaking outdoor PVC pipe or if you need to dig in your yard to install landscaping or other items, it's important to locate your pipes. Although you can pay someone to find your pipes, it's not difficult to find them yourself if you have several hours to spare. It takes trial and error, but the steps are fairly basic and don't require expensive tools.
Mark potential pipe lines and note where faucets or other outlets are located. Mark a straight line between the outlets and the street or your home. Draw a map of your yard on paper and mark potential pipe lines on the map as well for reference. When you locate the pipes, mark those lines on the map differently from potential lines.
Press your probe rod into the ground along the marked potential lines. A probe rod is a T-shaped device with a simple handle on top of a straight shaft. Hold the handles and press the probe down into the soil. Start near the faucet or other water outlet, since you know for sure there is a pipe there. If you see water bubbling up from a leak, start near the supposed leak with the line-of-sight toward the house. If you don't immediately hit a pipe, insert your probe rod a few inches to the left and then to the right until you find the pipe. Sprinkler pipes are often 8 inches below the surface, but main supply lines can be up to 18 inches below. Although it takes time and some trial and error, probing is a simple and inexpensive way to locate plastic pipes underground.
Dig with a shovel along the assumed pipeline. If you didn't find a pipe with your probe rod, use a shovel to dig small holes. If you think you have a leak, using a shovel might be quicker than the probe-rod process because you can find the leak and the pipe at the same time. Make shallow, angled pushes with the shovel to make sure you don't break the pipe when you find it. Dig several holes along the line to make sure the pipe doesn't turn. This is very time consuming and will require you to fill in the holes after the pipe is located, so be sure to try the probe-rod procedure first unless a leak is obvious.
Rent a pipe locator from a tool-rental company. These radar devices are relatively user-friendly---typically, turn it on and roll the device across the ground where you think the pipe may be buried. The screen will display possible pipes; audio-only versions will make a distinct tone when possible pipes are located. Some more expensive pipe locators work in conjunction with a thumper, which vibrates the ground to make the radar devices work more quickly and accurately.
In the United States, call 811 to have all existing buried utilities marked. This won't find sprinkler or other pipes, but it should find the main water line.