We always put a ball valve directly to the tank port so we can service the water trap and oiler without draining the compressor. It's also nice to shut that off for safety and to preserve the full tank of air the compressor generated without worrying about it bleeding down. Then we are good to go the next time we need air without restarting the compressor. When you get to be an old fart the hardest thing is remembering to close the valve when you're done...LOL