Which component is key in preventing backflow in plumbing systems?

The key component in preventing backflow in plumbing systems is the check valve. Check valves are designed to allow fluid to flow in only one direction, thereby preventing any reverse flow that could compromise the system. They are critical in maintaining the integrity of water supply lines, especially in scenarios where a change in pressure may cause water to flow backward, which could contaminate clean water supplies or disrupt the system's function.

The other components mentioned serve different purposes. A pressure gauge is primarily used to measure the pressure within the system and does not actively prevent backflow. A pump motor is essential for moving liquids through the system but has no role in managing backflow. A service valve is used for isolating sections of the plumbing system for maintenance or emergency scenarios, but it doesn’t inherently prevent backflow in the way a check valve does. Thus, the check valve is specifically engineered for backflow prevention, making it the correct choice.