Malcolm,

Like others, I've used ABS pipe (4-inch) and tapped one of the ends for NPT to hose barb fittings. I also agree with the other comments that a resin trap usually isn't necessary for bagging thin hand layups. I did run into an issue with ABS while doing vacuum infusion, where enough resin entered the trap to melt the ABS when it kicked off. I found the problem when the bottom of the trap collapsed and started leaking air into the bag. After that, I put the trap in a bucket of water - and learned to control the resin better!

http://www.thag-o-mizer.net/infusion_page1.html

Sam