Temperature and pressure relief (TPR) valves are critically important safety devices.
When one fails or is improperly installed in a way that prevents it from doing its job, a traditional tank-style water heater can behave like a bomb (or a rocket). Here, a flush kit for a tankless water heater is installed upside down, placing a shut off valve between the hot water output and the pressure relief valve. While the small amount of water in a tankless water heater would cause a less “exciting” failure, accidentally closing the valve could still create a dangerous and/or expensive result.