Blowing out moisture from gas line to furnace

So, because of budget reasons when building the garage, I used 1/2" black pipe for the line from the house to the detached garage. Up the wall into the storage space is my furnace. Ten feet before the furnace connection I put a vertical drop cleanout or moisture trap. If I open the trap will I get most of the moisture out? I believe that moisture, every year at startup, causes a delay of the furnace to kickon that takes about 24 hrs. Is this normal?