An engineer has been out to my central heating he has said that we need to flush the system to get rid of a blockage as the radiators and shower go hot & cold can you tell me how to do this has their does not appear to be a drain valve on the down stairs radiators

V Potts, April 2009

If your system is sludged bad enough to cause those problems with hot water it may not be repairable without replacing the secondary heat exchanger. best thing to do, other than getting a profesional powerflush done, would be to add some system cleanser to the system such as sentinal X400, or fernox, and run the system for upto a month then fully drain down and refill. if there's no apparent drain off on the sytem you may need to remove a radiator and do it from there.

andy gas man, April 2009