Problems which indicate your heating system requires radiator power flushing are:
Small leaks coming from the radiators, pipe work or unions
Inconsistent or no hot water
Boiler keeps cutting out
Dirty water in radiators (check by bleeding a radiator)
System slow to heat up
Boiler making a knocking or banging noise
Radiators which have any cold spots are likely to need radiator power flushing
Noisy pump or repeated pump failure
Any of the above symptoms could indicate that your heating system has circulation problems due to the build up of limescale, sludge or corrosive deposits in your
system and would therefore benefit from radiator power flushing.
Radiator power flushing is a simple process, but it is recommended that a heating engineer carries it out for you to ensure the central heating cleaning is completed safe.