How to recognize a defective expansion vessel?
Signs of a defective expansion vessel include a frequently dripping safety valve, uneven pressure, and gurgling and cold radiators. However, it should be noted that these side effects can also have other reasons, which is why there are methods to check whether an expansion tank is actually defective or not.
Methods for checking
You can determine if an expansion tank is defective or not by the sound it makes. If there is a hollow sound from about halfway along the expansion tank, everything should be in working order and there should still be enough gas. If, on the other hand, a muffled sound occurs along the entire length, the membrane has ruptured and water has flowed into the vessel.
In this method, you open the valve on the front of the expansion tank with a pin, it is the same valve that is used in bicycle tires. If only air escapes, there is still gas in the vessel. If water escapes, the membrane is already ruptured. You should also pay attention to the color of the water. If the water is brown, corrosion has occurred in the system.
The DIN 4807-2 specifies an annual inspection of the expansion vessel.