What device is used to ensure that a pump is running in a hot water system?

In a hot water system, a flow switch is crucial for ensuring that a pump is operating correctly. Its primary role is to detect the presence or absence of water flow within the system. When water flows through the pipes, the flow switch activates, signaling the pump to run and circulate the hot water. Conversely, if there's no flow detected—often due to a closed valve or a malfunction—the flow switch can deactivate the pump, preventing potential damage from running dry or overheating.

This function is particularly important in maintaining the system's efficiency and safety. In contrast, the other devices listed serve different purposes. A temperature sensor monitors the temperature of the water but does not control the pump's operation directly in relation to flow. A pressure regulator is responsible for maintaining consistent pressure within the system, ensuring that the water pressure remains within desired limits but does not indicate pump activity. A water hammer arrestor mitigates shock waves from sudden changes in flow within the piping but does not interact with the operational status of the pump.