Why would you need a trap on this drain line? Doesn’t it just empty into a floor drain?
If water is coming out of the furnace somewhere other than the drain line, then the drain line is clogged. Take the drain pipe off the furnace and run a coat hanger inside the drain hole of the furnace.
I question why it has a trap also. I did some googling and appeared many have it...idk why. I took the drain pipe off for the night and have it draining into a bucket. See if that dries it up.
