Noisy central heating system

[Hannahb]

We had a new boiler and thermostatic valves installed 18 months ago. Made it a sealed system and fitted a pressure gauge and, I think, disconnected a small tank in the attic? Central heating (CH) was no problem last winter except pressure kept dropping. In spring found 3 very small leaks at valves. Installer no longer Corgi-registered so used another plumber to fix leaks. Since then CH makes loud "trumpeting" or "fog-horn" noise every now and then. Stops if I turn down the main thermostat in hall or one of the radiator thermostats. Frightening noise as sounds as tho something's going to blow up! Noise definitely sounds as though it's coming from the attic (where our cold water tank is). Not sure what this would have to do with it if it's a sealed system?? Has anyone any ideas? Too vague for my plumber to be able to diagnose the problem as I can't make it happen to order when he's here! Thanks

[terence7556]

where is boiler positioned? also did you have to pay for leaks to be fixed? i assumed corgi registration was for the gas element of the system i.e. boiler not to repair water leaks that were obviously there from the start and not picked up on commissioning
reason i ask about boiler position is, in the loft is not that unusual , where you say noises are from

[Hannahb]

Thanks for your help. The boiler is in the kitchen. At least one of the leaks was a direct result of new boiler as it was at pipe joint they made when fitting the pressure gauge. The company that fitted the boiler not only stopped being Corgi-reg�d but disappeared altogether � phone no. unobtainable and not in phone book. So I had to pay a new plumbing firm to mend leaks. Noise didn�t start till after leaks were mended. Plumber thinks one or more of the thermostatic valves may have been fitted wrongly (?upside down?). Interestingly, my mum�s house makes the same noise but only when she flushes the upstairs loo!! Nothing to do with her heating. And she can stop her noise by turning the cold tap on! My noise only happens when my heating�s on. All very strange!

[gasman]

There are many reasons for this type of noise. Water hammer or Valve chatter is one of them. Next time it happens turn off all the radiator valves to see if the noise stops if it does then turn them back on again one by one untill hopefully the noise starts again this will then identify the faulty valve. Turn it off again and try all the rest of the valves there may be more than one faulty. If the noise still happens when all valves are turned off than the Bypass or boiler valves may be at fault and need replacing
Or you could be suffering from what is known as Ketteling where the boiler heat exchanger has become scaled up and combined with air in the system make a terrible noise in this case get the system chemically cleansed and powerflushed. or replace the heat exchanger in the boiler.