If anyone is making their own trap, especially if you're pulling higher vacuum levels, it is a good idea to make it so you can open them up enough to be able to remove a stuck ball. They can really get deformed and wedged in the fitting at times.
Note also that if your moisture trap is in one location, but the pump is in another, and there is some distance between them (especially if they're at different temperatures), you can get condensation in the pipe in between them, so plumb them so liquid can flow into them from both directions in that case.
Final hint...a check valve between the pump and the moisture trap is a really good idea. Keeps the vacuum in your system from pulling air (or oil) from the pump back into the tubing system.
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