Along with gas, phone, electric and cable utilities, water and sewer pipes are an indispensable part of our underground infrastructure. Buried water pipes can be difficult to locate, however, whether you're performing a simple backyard project or planning a multi-million-pound office complex. Yet it's vital that you do locate those pipes before you start to dig. Randomly digging around is time-consuming and costly -- even dangerous. Many methods have been tried over the years to locate underground pipes. Some have been discarded; some still are in use; and others are new to the scene, employing the latest technologies available.
Check with your local council. Underground utility mapping is notoriously poor, or non-existent, but it's worth your while to start there. If it's a home location you're investigating, and the home is fairly new, there's a good chance that mapping exists. But even if it does, there's always the problem of "design" location versus "as-built" location, meaning that pipes often are laid in a different spot than indicated on construction plans. Major building sites often deal with decades of underground infrastructure, laid one project on top of another.
Use a simple thin, metal rod to poke into the ground if you have an idea of where the pipes are laid and at what depth. You can gently poke around and often can get lucky, especially in a small area like a background. The difficulty may be that, even after locating a pipe, you'll have a hard time following it directionally.
Figure out what material the pipe is, if possible. Knowing what year the house was built, for example, could reveal whether the pipes are be metal, clay, concrete or another material. Your trip to the local planning office may be able to help you with this fact, even if they can't help with the location of the pipes. Knowing the pipe's material will help you figure out what type of locator you might need.
Use ground-penetrating radar equipment if you don't know the composition of the pipes. These devices work on any type of material -- metal, concrete, clay or even PVC. The equipment can be purchased or rented, but they are expensive and aren't accurate for deeply buried pipes.
Use a radio detection device if you know the pipes are metal. The receiver detects electromagnetic signals emitted from metal pipes. This is standard equipment among companies specialising in utility detection. Companies have even begun attaching tracer wire and magnetic tape to underground pipes during construction so that detection with radio or other magnetic devices can be used at a later date.
Call a company specialising in finding water pipes. Aside from the techniques already mentioned, it can employ such methods as acoustic location, sondes or one of a number of newer-generation, handheld devices that employ a combination of acoustics and radio detection technology.
Believe it or not, dousing is alive and well and still practised by many. Dousing is the millennia-old art of using a forked stick or other similar device to locate objects -- water being among the most popular uses. There are many organisations dedicated to preserving and using the method.