Can a valve ever be installed between the relief valve and the boiler?

A valve should never be installed between the relief valve and the boiler due to safety concerns and code requirements. Relief valves are critical safety devices designed to prevent excessive pressure from building up within a boiler, which can lead to catastrophic failures such as explosions.

When a relief valve operates, it must have immediate access to the boiler to function effectively. Installing a valve in this line could potentially create a scenario where the relief valve cannot discharge properly when needed, leading to unregulated pressure buildup. This would compromise the safety mechanisms established to protect the boiler and those operating around it.

Regulatory codes and safety standards universally require that the discharge path of a relief valve be free of obstructions and comply with specific installation guidelines to ensure reliable operation during an overpressure situation. Therefore, it's crucial to maintain a direct connection from the relief valve to the boiler without any intervening valves.