Hiya - my brother has a Vaillant Combi gas boiler. When he turns on a hot water tap it'll only run hot for a few minutes (contents of reservoir probably) and then go cold. Does this mean that the heat exchanger is scaled or damaged? Can it be replaced or would the boiler itself need replacing? How can the problem be best remedied? What would cause such a problem?
Hi . this means that the small domestic hot water heat exchanger is sludged/scaled. It is easilyt replaced ,don't need a new boiler .
The heat exchangers do block after a while. If you want to limit how often it happens again then 1 flush the heating system including radiators and fit a filter , is magnatec. On the mains cold water coming into boiler fit an in line anti scale device. Could you please rate me ok or better , thanks