Unvented cylinder constantly sounds ‘on’

[Matt KB]

Hi,

I have an unvented cylinder and lately even without the boiler central heating or hot water ‘on’, the system sounds like it’s constantly ‘on’. All through the night, it used to be silent except when running, but now it can sound like it’s ‘on’ constantly for days at a time. Surely this cannot be normal, with what sounds like water etc. running through it?

Video of it in the middle of the night: https://youtube.com/shorts/v0WV6DHhsx8?feature=share

 

[Riley]

Check the tundish see pic. Is there water running through it.

 

[SJB060685]

Are you saying the boiler is constantly running? If so likely to be the end switch on HW two port valve stuck closed.

 

[Matt KB]

No sorry, the boiler is in its rest state. It is not on, as in active (so checking the Hive, no hot water and no heating on).
Yet randomly the cylinder is making that noise at points, like something is constantly running. At this point, the boiler is not showing as on, and still in its rest state.

 

[SJB060685]

Then as above look for the tundish and see if water is passing by first. If so it could be a couple problems.

 

[Matt KB]

Ah sorry, missed that post. Nothing in the tundish, that’s bone dry.

 

[Riley]

Does it stop if you switch off mains

 

[Matt KB]

I haven’t tried - do you mean the boiler mains switch or the electric mains in totality?

 

[SJB060685]

I think he means the incoming cold mains to property. Next I would be checking for any leaking taps etc on the hot side

 

[Riley]

Yes mains water

 

[Matt KB]

Ah, ok I’ve not tried that, however I did have a bit of a drip on the mains stock cock which has since stopped. Will try the next time it’s making a noise. Thanks.

 

[Gasmk1]

Does it have immersion back up if so has it been turned on by accident

 

[Matt KB]

It does have immersion backup but that is off at present. It's silent now, so will check when it makes a noise again if anyone has knocked it.