When de-winterizing an RV, what is the purpose of opening the faucet in the coach?

Opening the faucet in the coach during the de-winterizing process serves the essential function of allowing air to enter the plumbing system. This is critical because when you begin to fill the system with fresh water, it needs a way for air to escape, preventing any vacuum that could inhibit water flow. By doing this, the fresh water can effectively displace any residual antifreeze in the lines and reach all fixtures smoothly. This step ensures that the water system is operating as intended, without restrictions.

While some might think about flushing the system or removing leftover antifreeze, these activities occur after the air has been introduced to ensure a smooth flow of water. Opening the faucet is the first proactive measure to facilitate an effective and efficient de-winterizing process.