If you're planning on digging up your garden for any reason, you're going to want to know where your water pipes are. Performing any kind of construction without this knowledge runs the risk of damaging the pipes, which can flood your garden or your entire home and end up costing a lot of money. You can find underground water pipes in your front or back garden in a very specific way.
Buy a pipe locator device that is capable of finding both metal and plastic pipes. Depending on exactly where you're looking for your underground water pipes, as well as the area in which you live, they could potentially be made of either type of material. For the most accurate reading possible, you need a locator device capable of finding plastic and metal.
Set up your pipe locator as directed. How you do this will depend on what type of locator you own. For example, certain pipe locators make a noise -- typically with headphones -- when a pipe is found. Others display a on-screen indication that you're standing above a pipe.
Walk through your garden, aiming the sensor on the pipe locator at the ground as you walk. Your pipe locator will indicate -- either visually or audibly -- when you're standing above an underground water pipe. You can then mark the position of the pipe according to your own preferences.
Your local water company is responsible for all pipes between the water main and the boundary of your property. You are responsible for all pipes from the property boundary into your home.