Water pump running non-stop/water system problem

I pressurized the system with "city water" and I didn't hear anything running and it held pressure, even with the supply shut off, so I figured it wasn't my worst nightmare - a cracked pipe.

So call me a total noob... This year was the first winter I drained the hot water heater completely (rarely gets below freezing here.) So... You're right, the hot water heater hadn't filled up yet.

Thanks fort the help all. Vacation saved!!!