Temperature and pressure relief valves, also called T&P valves, are emergency safety limit devices that will prevent or relieve overheated water and pressure. Without a relief valve during an unsafe condition, the pressure inside the tank would rise to the point the tank may rupture or explode. This would cause potential damage to both people and property. Rheem water heaters are pressure tested to 300 psi and have a working pressure of 150 psi. The T&P valve is designed to open when the pressure inside the tank exceeds 150 psi, allowing pressure to vent safely. The T and P valve will also open if the water temperature reaches 2100 deg F. The valve will remain open allowing cold water into the tank until the unsafe condition is over.