Air gets hot when it is compressed and picks up moisture in the form of vapor. When it cools, the moisture it's carrying drops out of the vapor state and condenses on anything cooler than it is. Consequently, there is no point in having a dedicated water trap anywhere near the outlet of the compressor as the water vapor essentially passes freely through it.
I found an old post online regarding the use of metal pipe that zig-zags up the wall, peaks at it;s highest point near the 25 foot mark and has at least two downward pointing legs, one at the compressor outlet and one at the end source at least 50 feet down stream of the compressor side of the pipe.
The metal pipe cools the warm compressed air and the water condenses inside it, runs down from the peak and drops into the down pointing legs at each end where a ball valve can be turned to drain the water.
On the cool end of the pipes, another branch travels vertically up to a water trap just in case, and then out to the distribution set up you add.
I have never seen one drop of water in my water trap as 80+ percent of the water drains back towards the compressor=side down pipe and a few remaining drops drain down towards the cool end of the system.
I used 1/2" galvanized pipe. Copper can work harden and crack relatively easily, even when firmly mounted. Black gas pipe has no corrosion protection. I also use a flexible line to connect the compressor to my cooling pipe.
What I don't have a picture of here is the pipe slowly zig-zagging up the wal to a single high point, where the moisture can drain back down hill to my two ball valves to be drained. It's amazingly effective at drying the air, inexpensive and easy to implement. My water trap has never had a single drop of water in it, but I used one anyway just because.
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