An automatic water feeder on a boiler is a device that feeds water to the boiler tank. It does not feed any type of animal.
An automatic water feeder is an electric device that works as part of a boiler heating system to ensure that a safe level of water is maintained inside the boiler. A boiler generates heat by creating steam from water. The water feeder senses the amount of water inside the boiler, either as part of the feeder itself or in conjunction with a sensor in the boiler. When the amount of water inside the boiler drops below the manufacturer's safe operating level, the water feeder opens and refills the boiler to a safe level.