Therefore, the pressure in your heating system drops

Do you have an eye on the expansion vessel or if the safety valve releases water? Poor pressure in the heating system is often due to troublesome expansion vessels or a leaking safety valve.

It is usually said that a heating system can be divided into two types - closed and open systems. With an open system, you have an expansion vessel in the attic with a line up through the roof where air can be pushed out or sucked in as the water level in the vessel changes with the temperature. A closed system has an expansion vessel down in the boiler room. This vessel has a rubber bladder inside that can be compressed or expanded as the water in the heating circuit expands or decreases depending on the temperature.

If the expansion vessel is working fully and the pressure is only dropping at a slow rate, it is likely that there is a leak somewhere.

Safety valve and expansion vessel should be easily monitored to quickly detect any faults in the system. In the worst case, leakage from the safety valve can be mistaken for hidden leaks in the system.