My boiler / CH system is now 5 years old. I'm on my third heat exchanger (the lower one). Recently the system would only give me warm DHW and intermittently a little HOT water. I called the plumber in and he found that this latest heat exchanger was partially blocked up with black ferrous material. He managed to remove about an egg full by puffing and blowing, knocking and shaking the heat exchanger. System now works fine. Before leaving he suggested that I have the whole system Powerflushed and provided an estimate of between £600.00 and £700.00 for the job. This seems rather expensive to a layman like myself. Any advice from you experts? Is there an alternative to Powerflushing to clean the debris from the system? 
