Essentials 19 Litre Heating Expansion Vessel It is well known that water can not be compressed. Taking that as a principle, the volume of the system’s water increases along with the temperature increase in the closed circuit heating&cooling systems. As the increasing water volume can not be compressed, the excess of the water has to be compensated into the closed circuit system. For this reason, the most common way to compensate the excess of the water is to add an expansion tank to the system. When comparing, Essentials heating series expansions vessels in use at closed circuit system to open circuit systems, the expansions vessels provide great advantages to the system: ·The outside going water has to be added back into the system each time in the open circuit systems. ·Corrosion is quite possible in open circuit systems because of the oxygen penetrating into the system. ·The installation of the expansion vessels is much easier than the open circuit systems.