What role does an expansion vessel play in a sealed hot water system?

An expansion vessel is a crucial component of a sealed hot water system, primarily designed to absorb excess pressure that can occur during the heating of water. As water is heated, it expands and this expansion can lead to increased pressure within a sealed system. The expansion vessel accommodates this increase by allowing some of the water to flow into it, thus relieving pressure to maintain the integrity and safety of the system.

This function helps prevent potential damage to pipes and fittings, or even catastrophic failures due to excessive pressure buildup. The expansion vessel typically contains a diaphragm or bladder that separates the water from an inert gas, usually nitrogen, which absorbs the pressure as it fluctuates with the water temperature.

The other options represent functions that do not align with the purpose of an expansion vessel. While maintaining a constant temperature is important for a hot water system, it is typically managed by the thermostat and heating controls. Filtering harmful bacteria is not a function of an expansion vessel; that role would typically fall to water treatment systems or filtration systems. Lastly, reducing water flow is not relevant to the function of an expansion vessel, as it is designed to manage pressure rather than regulate flow. Thus, the role of absorbing excess pressure is essential for the safety and efficiency of a sealed hot water system