What is this noise and how to stop it please ?

[scooby1]

Periodically we get a noise when we turn on any hot tap if no hot water has been drawn for 6-8 hours. It's a house that we had built 8 years ago, I think the system is called an "unvented system" i.e. there is no header tank with the traditional ball valve, just a large tank in a cupboard in one of the 1st floor rooms as per the image below. The smaller tank on the left is one that periodically I have to pump up to about 40psi as instructed by the plumber.

The noise only lasts for a few seconds but it's quite loud. Our plumber has been and stopped it before but if I know what to do I will do it myself. I am reasonably handy but not a plumber ! Really would appreciate any help. Thank you.

 

[muggles]

You need to be G3 registered to work on this I'm afraid. Call someone who has the correct qualifications

 

[scooby1]

You need to be G3 registered to work on this I'm afraid. Call someone who has the correct qualifications

Is it really that complicated ?

 

[undertrained]

Is it really that complicated ?

Not necessarily complicated, just legal.

It depends on what noise is and if it’s definitely coming from your cylinder, if it is then as per Muggles, you need a G3 registered engineer.

 

[scooby1]

Not necessarily complicated, just legal.

It depends on what noise is and if it’s definitely coming from your cylinder, if it is then as per Muggles, you need a G3 registered engineer.

Thank you. I'll record the noise and give access to it later.

 

[scooby1]

Obviously it depends on your volume level when you listen to this but this is the noise recorded inside the cupboard. Apparently I can't load a .wav or .wmv file here so I've put it onto YouTube :