I only want to apologise to gasguru about my daft post earlier i have been informed your very helpful ,can you help me with this proplem combi its a biasi when i went no heating h/w ok ,i checked it over and it would fire pump runs faN OK BUT 10 20 SEC CUT OUT now h/w is down its a condenser could it be that the overflow pipe has been put into the ground supposedly a drain away made but i didnt think until before if the pipe is blocked the boiler wont work will it the water stayed on 2 days longer any ideas thanks