A red expansion vessel is a small tank used to protect closed (not open to atmospheric pressure) water heating systems and domestic hot water systems from excessive pressure. The tank is partially filled with air, whose compressibility cushions shock caused by water hammer and absorbs excess water pressure caused by thermal expansion. Expansion Vessels operate on the basis that the internal chamber is separated by a rubber membrane, inside this membrane sits the water and surrounding this sits a pocket of air. As the water inside the sealed system is heated the water pressure increases, as water is non compressible the air inside the air chamber of the Expansion Vessel will become compressed thus leaving the system safe from over pressurisation. As water can increase by 4.5% volume when heated from 0-100 °C an Expansion Vessel is a vital part of any sealed heating system.
Absorbs excess water pressure
Ideal for central heating systems
Operates between -10°C and +100°C
Stops systems becoming over pressurised