Which two types of valves are required on a feed water line that delivers makeup water to a hydronic boiler?

The correct choice emphasizes the importance of controlling water pressure and managing the flow of makeup water effectively in a hydronic boiler system. A hand valve is crucial for manual control, allowing technicians to open or close the water flow as needed during maintenance or troubleshooting. This manual intervention is vital, especially in systems where precise control is necessary.

On the other hand, a pressure reducing valve is essential to ensure that the incoming water pressure is regulated to an appropriate level before it enters the boiler. Excessive pressure can lead to operational issues, inefficiencies, or even damage to the boiler. By maintaining a safe and optimal pressure level, the pressure reducing valve protects the system and enhances its longevity and performance.

While other options include various valve types, they may not provide the essential control and safety required for managing the feed water in a hydronic boiler effectively. Thus, the combination of a hand valve and a pressure reducing valve plays a critical role in delivering makeup water properly and safely.