1 the discharge pipe cannot be directly connected to the home s plumbing drainage system but an air gap located in the same room as the water heater can used to connect to the drainage system.
Water heater pressure relief valve discharge pipe.
Temperature pressure relief or tpr valves are safety devices installed on water heating appliances such as boilers and domestic water supply heaters.
Building codes require temperature pressure relief tpr valves with discharge pipes on all new water heater installations.
Just image the power that can be generated when the water starts to boil inside the tank.
If the pressure in the tank exceeds 150 psi or the temperature exceeds 210 degrees fahrenheit the tpr valve opens to release the pressure.
An air gap eliminates the possibility of backflow from the drain into the discharge piping.
This is to prevent a potentially catastrophic failure.
If temperature sensors and safety devices such as tprs malfunction water in the system may become superheated exceed the boiling point.