Air compressor drain valve

[Snapon1]

I was wondering if it is best to leave your air compressor drain valve open or closed after draining?

 

[The Cobbler]

closed so you don't have to remember to close it when you power up your compressor

 

[Citation]

Draining is important, leaving the drain open isn't. Once the water is out close it back up.

 

[MadMechMaster]

I only ever leave it open long enough to stop spitting. Leave it charged up, you paid to put it under pressure.