To ensure optimum performance, clean the central heating system at least once per year. One can hire a professional heating service in Crawfordsville to do the job more efficiently.  In the case of power flushing, it depends on the sort of radiator you have, the age and type of boiler you have, and the hardness of your water. The quick and simple answer is that your radiators should be flushed every 5 to 6 years.