To detect an outdoor water leak, turn off all items that use water, such as the sprinklers and dishwasher, and turn off the home's main water supply valve. Write down the meter reading, and check the water meter in one to two hours. If the water meter reading changes, an outdoor water leak is present. To locate the leak, examine the property for standing water or areas that appear unusually damp or muddy.
The home's main water valve is typically located near an outdoor faucet, but can connect to any plumbing that connects the home to the water meter. If the water meter doesn't move after turning the home's water supply valve off, the leak is located indoors.
Underground leaks typically cause patches of wet, muddy or sunken soil to appear. Holes may appear in the soil above the leak. Irrigation systems and backflow prevention devices are common causes of outdoor leaks. To check the irrigation system, examine the irrigation valve box for standing water, and check for leaking sprinkler heads with the system turned off.
If the backflow prevention device is dripping continuously, or a puddle appears under the device, replace it to fix the leak. Contact a plumber for assistance if the water meter test indicates a leak but the exact location of the leak is unclear.