Can anyone explain the gurgling sound from my boiler and what needs fixing?
It's a conventional pumped vented system with two motorized valves. The boiler, pump, controls, valves, HW cylinder and piping between them is recent (3 yrs), the rest of the system (rads) is elderly (probably 30+ yrs). Some rad pipeing is routed through concrete floors. At this point, I hear the sucking of breath through teeth.
The feed and expansion pipes join together in the airing cupboard a few feet below the header tank (which is in the loft) and the single pipe joins the system in a tee with the other branches being the flow from the boiler and the inlet to the pump. The pump outlet feeds the two circuits through motorized valves with a partially closed gate valve acting as a bypass (all rads are TRV'ed).
The heating circuit is always off at this time of year so only the HW cylinder is being heated.
The boiler seems to gurgle and there is often a gushing sound from the pump.
It sounds like air but where is it coming from?
There are no detectable leaks (ie no wet floors or ceilings).
The hot water is heated as expected and the system turns on/off under control of the cylinder stat as expected.
The level in the expansion tank doesn't seem to change much. The water in there doesn't get hot, does that mean it's not pumping over?
Andrew