What is the first step in draining a water system during winterization?

The first step in draining a water system during winterization is to close the main shutoff valve. This action is crucial because it prevents any additional water from entering the system while you're in the process of draining it. Closing the main shutoff valve ensures that the system is isolated, allowing for a more effective and thorough drainage of any remaining water within the pipes. This is particularly important in winterization to prevent freezing and potential damage, as any trapped water could expand and cause pipes to burst in cold temperatures.

Although other steps, such as opening faucets or disconnecting unions, are also important in the draining process, they are typically performed after the main shutoff valve has been closed. By ensuring that the water supply is completely shut off first, you establish a controlled environment for safely draining the system.