Originally Posted by oldred
The pipe must be routed in such a way that the water that collects on the walls will drain down into collection 'drops" where it will remain undisturbed by the air flow until it is drained. This may sound complicated and hard to do but it really is quite simple and has been covered here a bunch of times in detail so do a search first on "air lines" and maybe one on "compressor" and you will find in recent posts some info on how to do this.
Your air line should slant slightly toward a 'drop' which would be, at least in my opinion, a tee (T) with the airflow going along the top part and a length of the hard line going down with a plug for easy drainage (this is essentially an improved version of an aforementioned setup). And if you have an air distribution setup with the lines going around the walls, have a real quality air dryer at the 'outlet'. Using a clean air hose is a good idea, sitting on the floor unplugged they probably get alot of junk inside of them, perhaps also some air tool oil? (put oil into air tool, plug into line, and some oil seeps back into hose and forms dirt holding residue is my theory)
The little disposable filters right by the gun isn't a bad idea either.