Where does it seem to be leaking from? The boiler holding tank? The flanged connector to plumbing Union? The Flange gasket? Is the water running down by gravity from above? Is there a steam trap that is loaded and venting? Is there a condensate return line trapped? How high is the high side of the temperature setting? Are you using the steam, or is it evaporating without cycle?
: Combi boiler seems to be leaking and i have to top up system manually is this a problem with the boiler or a leak in surrounding pipes