On Mon, 30 Apr 2007 17:41:08 GMT, B A R R Y
wrote:


What if it takes my compressor a week or two to drain down, so there's a
sizable change I might use the energy? If I have half left, I use half
as much enegery refilling the tank.


Leave the tank pressurized and shut power off to the motor.

The normal failure mode of a tank pressurized within specifications is
to develop a pinhole leak, not to explode catastrophically. So there
is very little risk in leaving it pressurized. Understand that is not
the case if the failure is due to overpressurization. In that case,
the failure can be catastrophic so make sure the pressure relief valve
is properly set and functioning.