I once worked in a small Lathe / Milling shop. Had a big air compressor, bath tube size tank. Placed in the attic of the building, above the shop.
This was running for years... the boss dont belived in Maintanance.
One day, Water cames out of the air guns. No Kidding.
Turns out, the whole Compressor Tank was FULL with water! The funny thing was to empty it. Hauling a big floor jack and a big pan the steep stairs up under the attic, then jack the compressor up so you can slide the pan under it, let water flow in the pan, when full, pull the pan out, empty the pan with buckets, going downstairs and empty the buckets, repeat many times.
Great fun.
Idiots. Connect a hose and use air pressure to push the water up and out....