How many check valves are to be installed on the water supply for water heater #1?

The installation of two check valves on the water supply for water heater #1 is often required to ensure proper hydraulic control within the system. One check valve is typically installed on the cold water supply line feeding the water heater to prevent backflow into the municipal water system or other connected lines. The second check valve is crucial for maintaining the system's integrity by preventing any potential reverse flow from the water heater back into the supply line, which could occur during pressure changes or maintenance procedures.

Having two check valves helps create a safeguard by ensuring that any potential contaminants are blocked from entering the clean water supply and that the heated water does not flow backwards into the incoming supply. This is particularly important in systems where there might be other draws or where multiple water heaters are connected, ensuring that each unit operates efficiently without cross-contamination.

While fewer check valves could still function under certain conditions, the two-check-valve setup is a common practice in plumbing codes to enhance safety and reliability, making it the correct choice in this case.