Just to help the OP understand. Your video shows a duel fuel setup where the heat pump coil is on the bottom (upflow) and you can see the p-trap that was installed. The upper drain connection (that uses the tee fitting) is for condensate from the high efficiency furnace which has its own internal trap. From his description its sounds like he has an ac coil on top of furnace and that the AC coil drain uses a 'tee' fitting. Just guessing.