valliant eco828 combination combi system..pump fault ?

System water may be dirty as engineer suggested. Was the boiler fitted on to an old radiator system? You could try flushing the system with a cleaning chemical. After the chemical has done it's job, drain and re-fill the system to get rid of the chemical. Once that's done add some inhibitor chemical (not too much as this can do more damage than good). If system is very dirty you could try having a powerflush carried out.

Ian
July 2009