Could your system benefit with a power flush? Keep warm this winter and bring a new lease of life to your existing system whilst making it more efficient.Do some or all of your radiators need regular bleeding, if so they could be rusting away from the inside and the air you are releasing is hydrogen. Are they rusty or pin holed through, if so they will need replacing, but the rust from this will be throughout your system, blocking the flow of hot water through the system.Repeated failure of the pump - the black sludge in the system makes the pump struggle and burn out.Repeated replacment of the heat exchanger / hot water is slow to get to temperature - the heat exchanger is becoming blocked or is blocked with black sludge due to it's small water ways the water needs to be clean for it to be as efficient as possible.A properly cleansed and protected system will last for many years with less component failures.