The Junkers boiler expansion vessel absorbs pressure changes in the boiler due to the increase in water temperature when we heat it, thus preventing the maximum pressure at which our system can work from being exceeded and avoiding problems in our appliances or circuits and their wear due to excess pressure.

The pressure is determined by the safety valve. The normal working pressure of a heating system is around 1.5 bar.

In case of malfunction, to check if the internal diaphragm of the expansion vessel has ruptured or punctured, simply operate the internal valve mechanism by applying pressure to the valve core with a tool, such as a screwdriver, and observe what air comes out. If water comes out, it means the internal diaphragm is ruptured and the water has completely filled the vessel; however, if air comes out, the diaphragm should still be intact and it is only necessary to recharge the expansion vessel with gas or air.

You can also check the pressure in the tank using the pressure gauge on a tire inflator. This process should be done with the boiler or system empty of water to obtain an accurate reading of the air pressure.