When must a relief valve be installed in water heating appliances?

A relief valve must be installed in water heating appliances whenever heating water to ensure safety and compliance with building codes. The primary function of the relief valve is to prevent excessive pressure buildup within the tank. As water is heated, it expands, and without a proper release mechanism, this expansion can cause the tank to fail or even explode due to increased pressure.

This requirement is critical for all types of water heaters, regardless of their capacity, because safety standards are designed to protect users from potential hazards. While there may be specific considerations for high-capacity tanks, the need for a relief valve is fundamental to the safe operation of any water heating appliance during the heating process. Therefore, this option is rooted in both practical safety measures and regulatory compliance.