Just recently we have started getting intermittent water hammer from the CH pipes. It's an old system, at least 25 years. New World backboiler, pumped ch, gravity dhw. Serviced annually and works well enough. (yes, I know it's time for a change). The noise always comes from the same place, under kitchen floor about 2m from the boiler. I presume this is the return to the boiler and probably the lowest part of the system. AFAIK the pump is between the hammerpoint and the boiler Any ideas for a cure please? I am thinking it may be a build up of sludge/muck. If so, what do I do about it? System hasn't been drained for a couple of years and inhibitor was mixed in at that time. Touches wood ~ heating continues to be ok.
Thanks
Nick.