What does a pressure-relief valve on a water heater respond to?

A pressure-relief valve on a water heater is designed to respond to both pressure and temperature to ensure safe operation. The primary function of this valve is to release excess pressure that can build up within the tank, which may occur if the water within gets too hot. When the temperature rises, the water expands, leading to increased pressure. If the pressure exceeds safe levels, the valve opens to release the excess pressure, preventing potential tank rupture or explosions.

Additionally, if the water temperature exceeds a certain threshold, the pressure-relief valve will also engage to help regulate this potentially hazardous situation. Thus, it operates as a safety mechanism, addressing both key factors—pressure and temperature—to mitigate risks associated with overheating and over-pressurization in water heating systems.