my auto drain looks a lot like this one. my tank is an upright version and has a drain bung right in the middle on the under side, where water would puddle inside. I used a T fitting and ran the drain on one side and a manual drain on the other side. the air outlet on the tank is about 1/2 way up. that runs up to the horizontal U shaped copper line that I have sloped to a drain at the end to form a low spot. that low spot is also plumbed into the auto purge drain. from the copper line the hose runs downhill to the vertical wall mounted 2" pipe that works as the next water separator. the air comes in the lower 1/3 of the pipe and exits near the top. the volume of the pipe slows the air movement so the condensate can form on the walls of the cool pipe and run down. another reason for using the copper pipe is because it absorbs and gives up heat quick. same for the reason behind the distance to the wall mounted pipe, the air has a chance to cool down. the wall mount also has a drain line at the bottom connected to the auto purge. if doing it again I would look for some heating "fin". it is a copper or steel pipe (depending on the size and your spec) that has fins all around the outside. used for baseboard heaters etc. that would shed heat quicker than just a copper pipe. same for the wall mount, the "fin" comes in pretty large sizes for commercial applications. I have also installed a large pressure gauge in the system that is easily read from a distance. that helps when you are sandblasting or painting etc. you know what the compressor is doing. the wall mounted pipe looks like the the second link. there is also a desiccant material that can be used inside it. from the wall mount the air runs through a valve and out to the shop system. I used black pipe to plumb but would use pex next time. when I did my system there was nobody who could say for sure if the pex connections would withstand air pressure. pex is easy to work with and doesn't rust....my system has a hose reel at the vice, one at the solvent wash tank and one on each side of the double garage with another in the middle. 5 all together. there is an outlet with quick connect between the single bay doors as well. each reel has a condensation drop out plumbed in where the pex line connects that feeds the reel. no auto purge on those though. the compressor is sitting sideways so it has good fan cooling air flow through and not blowing air at the wall.
that pretty well describes my system I think. each run slopes to a drain placed where access is easy.
https://www.amazon.ca/Electronic-Aut...8&sr=8-50&th=1
https://www.princessauto.com/en/air-...t/PA0008055757
https://www.princessauto.com/en/air-...t/PA0008506206