An apparatus generally including a housing, a power source, a temperature sensor, a display and a circuit. The housing may have a bore adaptable to receive a flow of water. The power source may be operational for generating electricity and coupled to the housing. The temperature sensor may be coupled to the housing and in thermal contact with the water flowing through the bore. The visual display may be coupled to the housing and configured to display a temperature of the water. The circuit may be powered by the electricity and configured to control the display in response to reading the temperature sensor.