What is an expansion vessel?
Expansion vessels are important components in most modern pressurized domestic hot water heating systems. They are designed to protect the components of the system from a build-up of pressure which could cause damage to the installation.
In most hot water systems, expansion vessels are filled with one-half water and one-half air. When the pressure builds up in the water system, that air becomes compressed to absorb any excess pressure which helps to protect the water system including the cylinder and pipework. When operating correctly, an expansion vessel will partially fill and empty depending on the demand and use of the hot water.
In simple terms, this means that when hot water heats up in the hot water cylinder, it expands, and therefore needs somewhere to head for more space. The expansion vessel provides this space with a bladder which acts like a balloon to expand and decrease in size depending on the use and heat of the hot water.
Expansion vessels can normally be found in any hot water system where the water is pressurized. This means when the water supply is supply by a water system that is pressured such as mains water supply or boosted water supply. This shows us that expansion vessels can be installed almost anywhere from dentists to hotels, schools or care homes.