What causes water to drip or dump from a Temperature and Pressure Relief Valve (otherwise known as a T & P valve or Pop Off valve)?
The Temperature and Pressure relief valve is a safety device that STATE INDUSTRIES, INC. installs at the factory on all our water heaters. It is designed to open on a residential water heater, for your protection, when there is excessive water temperature or excessive water pressure in the water heater. There are many things that result in conditions causing a T & P to release water. Thermal Expansion in a closed system is a common cause that is often the last to be considered. When water heats it expands, just as mercury in a thermometer expands rising up the scale to show you a person’s body temperature. If the expansion of the mercury were to exceed the capacity of the thermometer the thermometer would explode. When water heats in a water heater it also expands. The expanding water will typically push back into the supply line preventing excessive pressure from building inside the water heater. When a check valve (backflow preventor) or pressure reducing valve is installed (without
