I used to have a combination boiler and this was replaced a couple of years ago with a condenser boiler. I want to replace a radiator in the bathroom with a towel rail. I was just about to remove the radiator when I thought I had better check with diydoctor. Instructions on draining the central heating system refer to an open system only. It says for sealed systems I should get a plumber to do it. Is my system a sealed system? Does this mean I shouldn't fit the towel rail myself? There is no hot water tank in my system. The water is heated through the boiler.