Massachusetts Plumbers Journeyman Practice Exam

What are required on the hot and cold water inlets to the automatic central control mixing valve?

1. Ball valves

2. Check Valves

3. Gate valves

4. Pressure relief valves

The correct answer is: Check Valves

The correct answer is check valves. In the context of an automatic central control mixing valve, check valves are essential because they prevent backflow in the hot and cold water lines. This ensures that the hot water does not inadvertently flow back into the cold supply and vice versa, which could disrupt the intended function of the mixing valve and lead to inconsistent water temperatures at the point of use. Check valves also contribute to the overall safety and efficiency of the plumbing system. By maintaining the direction of flow and preventing cross-contamination between the hot and cold water systems, they help uphold water quality and user safety. Other options—such as ball valves, gate valves, and pressure relief valves—have their specific purposes in plumbing systems. Ball valves and gate valves are primarily used for isolating sections of a plumbing system and do not necessarily control backflow. Pressure relief valves are designed to protect systems from excess pressure, not to manage flow direction. Each of these components serves important roles, but in this scenario, check valves are necessary for maintaining the integrity of the water supply to the mixing valve.