What is the term for the loop arrangement that prevents water in a boiler from being forced below a safe water level?

The term "Hartford steam loop" refers to a specific piping configuration used in steam boiler systems. This arrangement serves an important safety function by ensuring that water levels within a boiler do not drop below a designated safe level. Essentially, it involves a pipe that connects the boiler to the return line from the heating system, allowing for a small amount of water to flow back into the boiler, thereby maintaining adequate water levels. This loop is critical in preventing boiler damage or catastrophic failure, as low water levels can lead to overheating and potential explosions.

The other options describe various piping or control concepts, but they do not specifically relate to the function of maintaining a safe water level in a boiler as effectively as the Hartford steam loop does. The Hartford steam loop is a well-recognized standard in boiler design and safety measures, emphasizing its importance in plumbing and heating systems.