We are at your service with our expert technical service personnel and masters for our Boiler Repair Service. COMBI REPAIR SERVICE Anyone who lives at home with a conventional Combi Boiler knows that it is very useful and automatic. It works from a timer and the Expansion Tank maintains the water level in the system, as it should. However, Combi boilers are very different and many people do not know how to fill the water in the central heating system.