The Heatline expansion vessel is a product to handle the expansion of water in a boiler or hot water system due to increases in temperature. When water rises in temperature, it expands, particularly when it is placed under pressure such as in a sealed heating system or an unvented hot water cylinder. Expansion tanks typically contain a cylinder or disc which is divided inside into two compartments separated by a rubber sheet known as the diaphragm.

Brand Name	Heatline