A liquid separator will not remove uncondensed water. That's why I suggested putting liquid separator down stream of underground pipe. The water will condense in underground pipe then can easily be removed by low point drain and down stream water separator.
The 100ft downward sloping underground pipe actually functions as an effective water separator in itself (remember to keep it drained). With this long underground run it will render unnecessary a desiccant filter in most situations.
I have a desiccant filter system but have found it unnecesary for painting. My downward sloping Cu lines effectively removes the condensed water.
It wouldn't hurt to put an oil separator upstream of 100' line. I didn't and have not had a problem.
Last edited by 001mustang; 06-23-2009 at 04:37 PM.