What is the primary cause of thermal expansion in hot water systems?

The primary cause of thermal expansion in hot water systems is related to the fact that heating water increases its volume. When water is heated, its molecules gain energy and move apart, which leads to an increase in volume. This phenomenon is a fundamental principle of thermodynamics, where most liquids expand when heated. Therefore, in a closed or semi-closed hot water system, as the temperature of the water rises, the expansion can create pressure within the system that must be managed to prevent damage or failure.

Understanding this concept is crucial for properly maintaining hot water systems and ensuring that components such as expansion tanks and relief valves are effectively utilized to accommodate changes in volume and pressure as water is heated. This knowledge helps plumbers design systems that can handle thermal expansion safely and efficiently.