relief valve shut off hazard

The purpose of a pressure/temperature relief valve on a water heater tank is to open up and release water if the pressure exceeds 150 PSI or the water temperature exceeds 210 F degrees. Apparently the PT valve at this water heater was leaky and the homeowner fixed the leak by installing a shut off valve on the relief valve. This water heater tank is now a potential rocket ready to take off. Click here to view video of exploding water heater tank.