My house has central air with the air handler under the house and a drain line running out to the foundation drain. However, something odd I noticed is that the drain line has a "p" trap in it made from PVC pipe elbows and straights. As I understand it "p" traps are to keep gasses from coming back up the drain. Is this necessary on an air conditioner drain line? If it is I believe they make PVC traps for a straight horizontal line (it has slope but you know what I mean) that are much simpler. But I am not sure it even needs this. I wonder if the fact that it goes to a closed foundation drain has something to do with it. If I need the trap this is what I plan to use: What started this is I noticed that this trap got clogged. I disassembled and cleaned the trap and it drains now but I am sure this will happen again if I don't find a better solution. Thanks in advance.