Generally, in the United Kingdom, the cost of flushing a boiler system ranges between £300 to £700. The standard rate for power flushing a boiler in a small home is around £300. However, more extensive areas such as offices with about twelve radiators may cost up to £700. Since this cost is only to be borne once every five to six years, the rates are pretty affordable. In flushing a boiler system, if there are issues detected in some parts, the repair companies can charge an additional fee for changing them. Such as, the more radiators, the more the charges are. To fix every radiator, technicians can charge up to £20-30 for each additional one. Hence, radiator power flush costs vary, mainly depending on the number of radiators serviced.