Overflow is dry and we moved the expansion tank into the garage eaves from the loft during the conversion so we wouldn't have worry about any future problems.Tie up the ball valve on the F&E tank in the loft temporarily, in case the valve is passing slightly and generating a vibration. Are there any drips from the overflow of that tank?
No masts of any kind or heat pumps, honestly it's got me stumped. At first I thought maybe sound travelling down the chimney but you listen in the chimney. Total silence. In the corner of the room and you hear it. The corner is actually the middle of a back wall where it returns around the chimney but go into the loft and put your ear hard to the king span and not a peep. There is a radiator on the wall at the chimney but it's total silent.Is there a 5g mast nearby
No usb sockets. I actually de-energized the whole dwelling from the cut out and it still occurredIs it one of those USB sockets near ?
Turned it off at 2245. In bed for 10 mins and it's started. I'll be buggered if I know what's causing itTurn the stopcock off just before you go to bed tonight.
(fill a bucket with water for the loo first).
Definitely not the wind, it's still making the damn sound and I can hear it from the kitchen just nowOK, try again and this time empty the pipes, turn on all the taps upstairs too to be able to empty them.
IS it windy near you? could it be a chimney cowl in the wind?
Can't hear anything or feel anything if I put my hand on it. Tundish is dry. I did wonder if it was pressure related as now a few showers have been ran and sinks being used etc. The sound is gone.Relief valve lifting on your sealed system?
Nozzle
Eh not unless the whole household has spontaneously had hearing damage at the same time.Tinnitus ?

Turn off the water and electricity then depressurise the heating system. See it if is still there.Can't hear anything or feel anything if I put my hand on it. Tundish is dry. I did wonder if it was pressure related as now a few showers have been ran and sinks being used etc. The sound is gone.
Well the water has been turned off in fact did that again last night. I've already de- energised the whole property from the cut out to rule out an electrical problem but after the attic conversion all circuits were retested as part of the process. We had this problem 4 months ago after the conversion was completed and it miraculously disappeared. I put it down to air in the system. The only thing that comes to mind is the other half turned on the outside water pipe then realized the drain screw was still open and turned it off and tightened the screw then put it back on and since then it started again. I just put it down to coincidence.Turn off the water and electricity then depressurise the heating system. See it if is still there.

Well the water has been turned off in fact did that again last night. I've already de- energised the whole property from the cut out to rule out an electrical problem but after the attic conversion all circuits were retested as part of the process. We had this problem 4 months ago after the conversion was completed and it miraculously disappeared. I put it down to air in the system. The only thing that comes to mind is the other half turned on the outside water pipe then realized the drain screw was still open and turned it off and tightened the screw then put it back on and since then it started again. I just put it down to coincidence.
then depressurise the heating system.
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