I have a water pipe in my basement that runs off the main line to an outside spigot. It's only about four feet of pipe with a valve in the middle of it to restrict or allow water flow only to the outside spigot. When I turn the valve on to allow the water to flow to the spigot, but leave the outside spigot turned off, I can still hear constant running water in the pipe. No water seems to be leaking anywhere inside the basement from this short length of pipe. The outside spigot works fine if I turn it on but the running water sound from the pipe inside never stops. Only thing I can think of is the water is leaking in between the inside and outside walls, maybe? Any other ideas?