Do water traps work if horizontal?

Yes it must be vertical.
If it is horizontal then water can run back into the airline defeating the purpose of the water filter altogether.

Mike

Also, the drain valve isn't going to work terribly well in a horizontal orientation, I would think.

Al

QUOTE: Originally posted by neudog The instructions on the one i just purchased say that the filter has to be vertical to work properly. Is this absolutly necessary?

YES

Enjoy your modeling...

Like they said, they must be vertical to work. Also note that the airflow must go in a particular direction. One side is an inlet and the other an outlet, and it must be hooked up that way.

Thanks people, i guess those pesky instructions are there for a reason eh! i went to the hardware store today and got a 1/4' elbow so that i can hook up the filter vertical and lo and behold i see water in it already. Finally i have a workable airbrushing set up, no more wheeling the spare tire down the road... yay.