The Stop and Waste Valve is primarily used to:

• A. To Drain Water From a Line When Shut Off
• B. To Regulate Pressure
• C. To Prevent Backflow
• D. To Open Only Partially

Answer: (A)

A stop and waste valve is built to shut off a line and then provide a way to drain the water that remains in that section. After the valve is closed, the waste port lets the trapped water escape, making it ideal for winterizing outdoor or service lines and for maintenance work where you want the line completely empty. It isn’t used to regulate pressure (that’s what a pressure regulator does), nor to prevent backflow (that’s the job of a backflow preventer), and it isn’t primarily about opening the valve only partially. The drain capability after isolation is what makes it the best choice for draining water from a line when shut off.