The reasons for installing a magnetic filter in this way are two fold. Firstly, the filter will pick up any iron oxide sludge deposits, prolonging the life of the boiler and associated controls, pump and zone valves. Removing the iron oxide sludge deposits will mean that the efficiency of the boiler will be maintained and this in turn will prevent fuel wastage. They are an inline fitting taking only a short time to fit.
having said all that, like the builder says, Worcester Bosch are one of the best
and should give many years of use.