* What you have is a hot water pipe leak. The hot water surrounds the cold water pipe and transfers the heat to the cold water pipe.
* Test: Turn off all water usuage. Dot not flush the toilets nor have the washing machine going.
* Look at your water meter. It should not be recording that water is being used.
* If the water meter is moving, turn off the water valve at the water heater. Recheck the water meter.
* If the water meter is not moving, then you have a leaking hot water pipe.
* Turn water back on at the hot water heater.
* Eyeball the path between the hot water heater and the cold water tap.
* Listen along this path for a hissing or gurgling noise. Where you hear the noise is where the hot water pipe leak is.
* Good luck... Adios... Jasper...