What are temperature and pressure relief valves?
All storage type water heaters must be equipped with a properly functioning Temperature and Pressure (T&P) relief valve. These valves must be certified as meeting the requirements of the Standard for Relief Valves for Hot Water Supply Systems, ANSI Z21.22/CSA 4.4. The T&P relief valve is a safety device that serves two functions. It is designed to open and relieve water should the pressure in the water heater exceed the rated working pressure of the unit, 150 psi (1034 kPa). It will also open in the event that the temperature in the tank exceeds 210°F (99°C). If the T&P valve opens due to excess pressure, there will be either dripping or a small continuous flow of water that relieves the pressure. If, on the other hand, it opens due to a high temperature condition, the valve will open completely and allow the whole tank to empty until cool water resets the thermal probe on the T&P. Both excessive pressure and high temperatures in water heaters are extremely hazardous. Under normal wate
