Expansion tanks

Expansion vessel

— the expansion tank is a reservoir divided into two halves by a soft hermetic membrane (most often rubber): one half contains water, and the other contains air under pressure. Such tanks are installed in heating systems, and their purpose is to compensate for changes in the volume of the coolant that occur due to fluctuations in its temperature. Note that despite their high strength and reliability, expansion tanks should not be used in water supply systems: the water in them is in contact with metal walls, which is quite acceptable for technical use, but highly undesirable for drinking water.