On 27 Apr, 00:50, "Buck Turgidson" wrote:

I leave my Porter Cable air compressor full.
Does this do longterm harm to the machine?

In general, no. However a machine that has a slow leak down somewhere
and is going to be switched off for long enough to empty itself is
usually best vented deliberately rather than being left to do it
inevitably itself (or just fix the leak!)

You should of course always blow down the water after any sufficient
use of the compressor. This doesn't mean emptying the reservoir
though. Nor does it require doing if the reservoir has been left full
long-term with the compressor off, except possibly if you've had major
temperature changes.