A power flush machine is a tool used by plumbers to perform a power flush on central heating systems. It is made up of a large water tank; fitted with a strong pump and a magnet/s fitted either internally or externally.
There are several connections for hoses and valves to restrict flow or change flow direction. Two connect to the central heating as flow and return pipes and the other one is used to dump the dirty water down a drain.
There can be two more hoses connected; one for filling the machine and one for overflow to prevent flooding.>

The cleaning is done with a combination fast flowing water, chemicals and the use of magnets (sludge is metalic).
These machines cycle water at very large flow rates, but low pressure, around the central heating system.
This disturbs and moves the sludge down the pipes to the magnet/s, where it gets stuck and removed from circulation.
This procedure is done to prevent breakdown and damage to all the parts of the central heating system and to make it operate more efficiently.