A hot water heater leak alarm is a device that detects water leaks from a hot water heater tank. It consists of a sensor that detects the presence of water, a valve that shuts off the water supply to the heater, and an alarm that sounds to alert the user. The sensor is usually placed in the pan beneath the heater, and the valve is installed on the cold water supply line. When the sensor detects water, it sends a signal to the valve, which shuts off the water supply. The alarm then sounds, alerting the user to the leak. These alarms are important safety devices that can help prevent flooding and water damage.