The filter ALWAYS goes before the dryer to trap any oil that may be passed by the compressor. If you get oil on the dessicant, it will ruin it. If you fear the “crumble factor”, put another filter on the down stream side of the dessicant housing.
When piping your mains be sure to tap off the TOP of the line. You mentioned “pipe”. Is it copper or galvanized? Black pipe can be a problem if moisture gets in it. Copper is the way to go. At the very end of the main line have a riser with a blow down valve to “sweep” the main. An auto blow down valve on the tank is a nice thing to have. But if you blow the tank down once a week, you can save the cost of the valve. When you do your drops tap off the side of the line and have a “dirt leg” just for insurance. A strategically placed filter/regulator/guage(FRG) assy is a good idea too. These can be acquired in a “unitary” model.
-- OK, who's the wise guy that shrunk the plywood?
