Unexplained increase in your water bill. This is often the most obvious sign.
Wet or soggy spots in your yard even during dry weather.
A hissing or bubbling sound coming from the ground.
A sudden drop in water pressure in your home.
Potholes or sinkholes appearing in your driveway or yard.
Discolored water or a strange smell, which could indicate dirt or other contaminants are entering the pipe.