The Worcester Bosch 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, this expands, particularly when it is kept under pressure such as in a sealed heating system or an unvented hot water cylinder. Expansion tanks typically consist of a storage container or disc which is divided inside into two compartments separated by a rubber sheet known as the diaphragm.

Brand Name	Worcester Bosch