For safety, why should a shutoff valve NOT be placed between the relief valve and the boiler?

Placing a shutoff valve between the relief valve and the boiler poses significant safety risks. The primary reason is that it can create a dangerous scenario where pressure that builds up in the boiler cannot be relieved properly. When the relief valve is designed to release excess pressure, a shutoff valve could prevent it from functioning effectively, leading to potentially catastrophic pressure buildup within the boiler system.

Additionally, the presence of a shutoff valve in that location could lead to code compliance issues. Most plumbing and mechanical codes require that relief valves be connected directly to the boiler to ensure their proper operation during emergencies.

Furthermore, the installation of a shutoff valve may create a blockage in the pathway designated for pressure relief. This blockage prevents the necessary flow that is critical for keeping the boiler system safe under pressure. The relief valve’s primary purpose is to protect the system and prevent failure; any obstruction directly hampers its ability to perform that function effectively.

Together, these points illustrate why having a shutoff valve in this position is unsafe and problematic, confirming that all the listed reasons are critical safety considerations.