Found 3 inch PVC coupling to be leaking. Cut out leaking section and re-piped with new fittings. Also noticed that the horizontal pipe is pitch the wrong way. There’s no way to fix this because of the termination piece that goes through the roof. Vacuumed water out of emergency drain pan. Put insulation back on vent pipe Filter door is at the left side of the furnace 24 x 24 x 1