Which statement is true about a manual shutoff valve on the gas supply line?

• A. A valve installed on the discharge side is used as a shutoff valve.
• B. A valve on the gas supply line away from the appliance is used as a shutoff valve.
• C. A manual shutoff valve on the gas supply line is a common valve type used on appliances.
• D. A check valve on the exhaust is used as a shutoff valve.

Answer: (C)

Gas appliances are isolated from the supply by a manual shutoff valve placed on the gas line that feeds the appliance. This valve is chosen for its reliability and accessibility so you can quickly stop gas flow for service or in an emergency without cutting off gas to the entire building. That’s why saying a manual shutoff valve on the gas supply line is a common valve type used on appliances is correct. The other ideas mix up where the valve should be or describe devices that don’t serve as a true shutoff: the shutoff should be on the supply side near the appliance, not on a discharge side, a valve away from the appliance isn’t the standard location, and a check valve on the exhaust isn’t a shutoff valve.