It is sometimes the case that a hot-water apparatus works well until the water reaches the boiling point, when a rumbling sound at the tank is heard. This noise is merely the sound of the water boiling. The remedy is to regulate the boiler damper so that the water shall not boil. When the noise occurs, it can he silenced by drawing off some water at one of the hot-water taps. This causes cold water to flow into the tank and reduce the temperature. The fact that water has a tendency to boil indicates either the use of a more powerful boiler than the apparatus requires, or want of attention to the damper. The latter is the more probable fault, causing the boiler to become overheated and fuel to be wasted.