Condensation building up in the tank, causing internal rust, eventually
leading to tank rupture, is a long term possibility. Compressors have a
drain valve on the tank for this reason.

--
Lloyd Baker

"Buck Turgidson" wrote in message
...
Partially out of laziness, inertia, procrastination, and partially because
I use it several times a month, I leave my Porter Cable air compressor
full. Does this do longterm harm to the machine?