On 4/28/2018 2:01 PM, dpb wrote:

How does it let water out but not gas?

I'm pretty sure Ed meant "leg" not "let"; it's just a collection point
that keeps the condensate/entrained water have a place to go out of the
main line into the appliance; not an automatic outlet.


Correct. Instead of an elbow at 90 degree turn, they use a Tee and the
bottom has a short nipple and cap. Traps anything moving in the pipe,
liquid or solid.