Loud "cracking"noise from fairly new Hot Water Cylinder

[Bladevane]

As per the title but first a litle background.

We upgraded our gravity fed water system last year to a pressurised system which included a Joule Unvented Slimline Hot Water Cylinder, expansion vessel and all the trimmings. The installation was done by a pro and was so much neater and compliant than I could have achieved. It works perfectly.....but...has always exhibited a loudish "crack" when the water pressure decreases, like when the shower thermostatic valve is opened. The pro said not to worry. As I said, the system works perfectly and there are no leaks. I am still concerned that the cylinder is going through a cycle of pressure and therefore demonstrates this as a noise, a variance which is not something I am too happy about. After all, a cylinder is a static device and should not move, unlike a dynamic device which I would expect to grunt and groan a bit.

My question is, therefore, has anyone experienced similar noise and what was done (if anything) to eliminate it?

I have tried various pressures in the expansion vessel and the cylinder from 2 bar upto 3 bar. No difference. The cracking noise can only really be repeated when the system is isolated and the pressure drops to zero. Otherwise it's a bit random.

Thanks in advance.

 

[Slowcoach]

Can you call joule, can’t see a technical number specifically but see what they say.

 

[knighty]

I have 3x 300 litre hot water tanks at work, they're silent unless I cut the water feed to them and drain the pressure out, then they crackle and pop like crazy

I think there's something wrong... guessing you have mains pressure in through a pressure reducing valve (in case mains pressure too high for the tank) so there shouldn't be much pressure change in the tanks as you turn a tap on/off

pressure reducing valve might have a gauge on it, you could watch it while someone else turns taps on/off


I wouldn't be happy with it, noise means there's movement, could lead to cracks etc.

 

[Bladevane]

@Slowcoach - Thanks. I've tried Joule but get the robotic answering service - which in fairness is not bad, but not as good as I want.

@knighty - Agreed. Noise means something is moving - and it shouldn't be.

 

[DanZac]

Silly question, but is it the tank making the noise, or an associated part (pressure reducing valve, one way valve?) making the noise which is then heard through the tank (and possibly amplified)?

 

[addjunkie]

Is the bladder in the expansion tank shot…so not smoothing the pressure changes?

 

[Bladevane]

@DanZac - I think it's the cylinder. But of course cannot reproduce the noise when my hand is on it to feel it.

@addjunkie - Bladder is fine and only as old as the cylinder (12 months). It holds pressure and I can vary it from 1 bar to 3 bar.

I measured the cold feed pressure and although the data sheet told me it was factory set to 3 bar I found it at 1.9 bar. I increased it to 3 bar but no difference.
Just spoken to a human at Joule - he confirmed it should not be making a noise and has asked for a video so they can listen and act. Easier said than done though.

 

[waddycall]

Just checking - did you have no pressure in the cylinder when you set the precharge pressure in the vessel?
Best bet would be to measure the static pressure when the tank is cold, release the pressure and set the vessel a little bit lower than the cold static pressure to make sure the bladder isn’t blocking the inlet.
Also sounds like you would be all over this anyway but make sure there are no valves at all between the expansion vessel and the cylinder.

 

[MattF]

The pro said not to worry.

Have you asked him if he actually knows what's causing the sound?

 

[Tigman]

It's not the pressures relief valve letting go , is it ?

 

[Smallfry]

I installed ours two years ago. Makes no noise at all, apart from being able to hear the water flowing when standing near the tank.

Our mains pressure is stupidly high, at nearly 21 bar. Water company MDPE pipe, meter and fittings are rated at 16 !

Assume hot and cold have been balanced ? Necessary if you have any mixer taps, or thermostatic shower. Balance valve could be the source of the "crack"

Pressure should be maintained in the storage tank, even when taking off hot water. So there should not be any creaks or groans, which will likely end up as fatigue failure.

I set mine at 40 psi when cold, and the expansion vessel the same. I also installed the vessel with the water inlet at the bottom, so if the diaphragm does fail, it will still function.

I don't get why the installer thinks it is not a problem. It would be bothering me.

 

[Bladevane]

Thanks for all your suggestions and ideas. With the help of my glamorous assistant I have now managed to get a short video clip of the noise and have sent it to Joule for their consideration.