Now something that you guys may not know is to use an old house steam radiator as a water trap. You can pick them up cheap at building wrecker yards. They can hold a lot of pressure and usually all that is wrong with them is bad fittings and you will change all of that anyway. Plumb it so the air from the compressor goes into the bottom at one end and leaves at the top of the other. Depending on what type you find you may have to drill and tap a hole. You may even have to use a bung and this could be brazed on or silver soldered. Place it so that air can get to both sides and put a water trap down low at the outlet side or end, I have an automatic spitter valve on mine. Be sure to slope it about an inch toward the spitter. You will be surprised at how much water it collects.