Expansion Vessels available to order online for next working day delivery or collection from our trade counter in South East London. We are a leading supplier of expansion vessels for central heating systems and potable water systems including Unvented Cylinders. An Expansion Vessel [ sometimes known as an Expansion Tank ] is a small vessel which is designed to take the expansion from expanding water in a closed central heating system of from the water in an unvented hot water system. The Expansion Vessel has a dividing rubber membrane inside with the water on one side and compressed air on the other. As thermal water expansion takes place the diaphragm moves further compressing the air allowing expansion to take place. Typically in the UK Market on older Central Heating Systems the Expansion Tank would be in the loft which would take up the expansion from the Central Heating System.
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