Final answer:
The purpose of an outlet on a boiler is to permit the emptying of water or sediment in the boiler.
Step-by-step explanation:
The purpose of an outlet on a boiler is to permit the emptying of water or sediment in the boiler. It is not used to increase the pressure in the boiler, regulate the temperature, or prevent overheating. When water or sediment builds up in the boiler, it can affect its efficiency and performance. The outlet allows for easy removal of these impurities, helping to maintain the boiler's functionality.