The leak is most probably from where the steel hot water demand pin that pushes the DHW demand fulcrum arm exits the brass assembly with the dhw diaphragm in it. A new o ring in screw in fixture is part of the standard service kit, along with diaphragms and other wearing parts. It has mains water pressure on one side and a long travel, it wears and weeps. A completely whooshless boiler is most probably a dead fan. However, you need to find a good corgi man to discover for sure whats up. Vokera would give you the name of a qualified local, or you could take pot luck.
c
June 2009