Air lock noise from cold fill to tank in loft?
Run any hot water tap in the house for a minute, then air lock type noise comes from cold fill pipe that goes into large tank in the loft. Turn off hot tap then put any cold tap on full bore eventually helps to stop the noise (which goes on even when no water is being drawn). Is it low mains pressure, air in the cold pipe or what? What can I do to stop it happening please? Occurs mostly in the summer months. We have an old style boiler, hot water tank next to bathroom and large tank with expansion tank in the loft.