Bathrooms appliances such as heaters and power showers use reed switch based Flow switches to detect if the water supply has been turned on. As soon as the shower is turned on, the flow switch detects this and this signal is used to activate a relay that controls the instant heater. Some models also use this signal to turn on a pressure pump to increase the water flow rate. In addition to switching on the heaters, thermal reed switches are used cut in and cut out the multiple heaters that heat the water as it is pumped through. This is to ensure that the heat of the water is matched to the flow rate set, as a higher flow rate would require more heaters to be turned on. When the shower is turned off, the flow switch will senses this and turns the heater or the pump off. Such instant heater power showers conserve as much as 40% more energy than conventional tank based heaters.