An overheated or over-pressurized 30-gallon water heater is the equivalent to a stick of dynamite.

Without a working temperature and pressure (T&P) relief valve in place, a water heater can explode, causing property damage, severe injury or death. Every hot water heater, gas or electric, tank or tankless, is required by law to have a correctly functioning (T&P) relief valve. This crucial valve allows water or steam to escape from the water heater if the water temperature is too hot or the pressure is too high. T&P valves open when the pressure reaches 150 pounds per square inch (psi) or when the temperature reaches 210 degrees Fahrenheit.  

Water heaters are equipped with thermostats and electric water heaters have overload switches, but the T&P valve is the only protection against explosions and damage from both excessive temperature and high pressure. These conditions can occur - without warning - when  an agency or municipality raises its water pressure or if the water heater malfunctions.