Expansion Tank Noise

[budest]

Getting a knocking/thumping noise from my expansion tank every time I turn the cold water taps on and off in the bathroom and recently it's continued to make the sound even when I've stopped running the water for a few minutes. Notice it more so when I turn the water taps on and off quickly.

What do you think? Turn the TV up?

**Edit - Also started to happen when I turn hot water on/off but not as loud as with cold water. I assume this is because there's more pressure from the cold water inlet? Also the system is pressurised.

 

[budest]

If it helps I've uploaded a short audio file of the noise but to hear it you have to stick headphones on or be at a computer with speakers. This is due to using my phones recorder. https://www.dropbox.com/s/6yunzrprv5299wg/Water Noise 2.mp3?dl=0

 

[JohnD]

I see you have an unvented cylinder. It has to be serviced and maintained by a qualified person with the "G3" card. It has several safety devices. It is not a job for a DIYer or an unqualified plumber.
see http://www.citb.co.uk/awards/qualif...gineering/unvented-hot-water-storage-systems/

When was it last inspected?

 

[ree]

Sounds like the diaphragm is damaged - this will happen in expansion tanks but usually only happens after a few years service.

Tank replacement is probably called for so a certified plumber must do the very simple task of changing out the TET.

Before the plumber leaves the site, politely check that the TET is pressurised to the required PSI for your situation.

 

[simond]

Ah, the world of Zilmet, my favourite expansion vessel brand. You can't buy cheaper. 3 years old and finished.

There is a bicycle tyre (schraeder) valve on the top of the vessel. Undo the black plastic cap and depress the plunger to let a tiny bit of air/nitrogen out of the valve (there's a bag full of gas and this is the test point).

If air comes out, that's good. If any water at all comes out, expansion vessel is finito. Call a G3 fitter to replace it.

You will sometimes get a bit of noise from this and the combi valve in normal operation, if there is water leaking through the tundish (open drain connection next to cylinder) the expansion vessel is definitely shot.

 

[budest]

I see you have an unvented cylinder. It has to be serviced and maintained by a qualified person with the "G3" card. It has several safety devices. It is not a job for a DIYer or an unqualified plumber.
see http://www.citb.co.uk/awards/qualif...gineering/unvented-hot-water-storage-systems/

When was it last inspected?

Hi there,

I know the heating system (oil) was serviced in September but I am not sure if they serviced the expansion tank. I live in housing association rented accommodation and they are very good at getting things fixed so I gave them a call earlier today and registered my concerns. A plumber will be out with 4 days.

 

[budest]

Sounds like the diaphragm is damaged - this will happen in expansion tanks but usually only happens after a few years service.

Tank replacement is probably called for so a certified plumber must do the very simple task of changing out the TET.

Before the plumber leaves the site, politely check that the TET is pressurised to the required PSI for your situation.

House is only up 2 years +months. As I say the thumping noise is mainly heard when turning the water on and off quickly. For months I thought it was a loose plastic pipe under the floorboards that was moving about as I turned the water on/off. But a few weeks ago I noticed a dull thump even after the water was shut off. Didn't pay it much attention to the other day when I decided to look a bit closer and I traced the noise to the expansion tank.

 

[budest]

Ah, the world of Zilmet, my favourite expansion vessel brand. You can't buy cheaper. 3 years old and finished.

There is a bicycle tyre (schraeder) valve on the top of the vessel. Undo the black plastic cap and depress the plunger to let a tiny bit of air/nitrogen out of the valve (there's a bag full of gas and this is the test point).

If air comes out, that's good. If any water at all comes out, expansion vessel is finito. Call a G3 fitter to replace it.

You will sometimes get a bit of noise from this and the combi valve in normal operation, if there is water leaking through the tundish (open drain connection next to cylinder) the expansion vessel is definitely shot.

Found the plastic cap you were speaking about and I can confirm air is coming through it when opened and not water.

Is thumping noise normal for this setup when water is turned on/off quickly?