Thumping noise from expansion tank

Yulkmn · 10-08-2023 9:38pm #1

Hi,

Not sure if this was already talked about.. Sorry if it has been.

Does anybody know why I hear a thumping noise from my expansion tank when the dishwasher is on or my washing machine.. (Wont let me upload a video)..

I got a new expansion tank fitted today and the noise is still happening..

Can anybody help in telling how to fix this?

Thanks!

John.G · 10-08-2023 9:45pm

Where is the expansion tank installed?, have you got a unvented HW cylinder supplied from the mains or from a cold water storage tank via a pump, if so, its generally white, if its a boiler system expansion vessel it will be red.

Lenar3556 · 10-08-2023 9:47pm

A dishwasher or washing machine should have no connection to an expansion tank.

Could it be coming from the cold water storage in your attic?

The video would be good if you could send a link maybe?

Yulkmn · 18-08-2023 7:05pm

Hi Folks,

Thanks for the replies.

@John.G - I have both the red and the white one. I have the cold storage water tank in the attic.

@Lenar3556 its not comming from the storage tank in the attic, ive been up there but nope that all good.

Ill try and attach a video in the next comment here.

A plumber was here today and replaced the expansion tank again, and set the pressure accordingly on it, he also swapped out a valve but its still occuring when the washing machine is on rinse.

Yulkmn · 18-08-2023 7:07pm

https://streamable.com/dzckw6

Link to the video

John.G · 18-08-2023 8:05pm

Is the storage tank supplying a pump which supplies all the house requirements? (apart from the kitchen sink, which should be from the mains) and if so, you will have a unvented HW cylinder?, can you take a photo of the cold water supply into this cylinder showing all the valves, ie pressure reducing valve and expansion relief valve, also a photo of the label on the side of the HW cylinder.

The plumber replaced the white E.vessel?, do you know what he set the precharge (air) pressure to?.

Yulkmn · 18-08-2023 8:46pm

Thanks for the quick reply @John.G!

Yes, the storage tank is supplying the pump which supplies everything in the house except the cold tap in the kitchen.

Im not quite sure what photos you are looking for so here is everything I think you asked for, sorry in advance if they arent right.

He set the pressure to 2.3 on the white vessel/expansion tank.

John.G · 19-08-2023 6:45am

Some great photos there.

I have attached a few labels below as its years since I saw one of these. Its strange allright but I think I've read about similar symptons somewhere before, just a few more queries before scratching our heads.

To confirm that the W/machine & D/washer are fed from the balanced cold, can you shut off the cold feed (and pump) and confirm that neither fill now.

Also: Cylinder T&PRV setting. (written on end). The combination valve PRV setting, the volume of the E.vessel.

and: the pump type/model positive or negative head, photo of pump label.

What valve did the plumber also change (with E.vessel)?

Yulkmn Combination Valve Set Rev2.jpg

Yulkmn · 19-08-2023 8:47am

Hi @John.G

I can confirm that either of the two appliances fill after shutting that off.

Attached are the photos requested, i just didnt know where two find the: "The combination valve PRV setting" , so I've given it a guess.

Thanks!

John.G · 19-08-2023 10:19am

"I can confirm that either of the two appliances fill after shutting that off."

Are you saying that they both keep filling??, if so it means that they are fed directly from the mains or gravity fed from the CWST. If you are saying they both still fill then to confirm it (again) shut off the pump and shut off the balanced cold water outlet valve labelled 1 and test again.

The "combination valve PRV setting" is the white valve labelled "PRV with non return valve."

Edit: What is the volume of the E.vessel and what valve did the plumber also change?.

Yulkmn Combination Valve Set Rev3.jpg

Yulkmn · 19-08-2023 9:34pm

So sorry @John.G , I formulated my sentence wrong this morning.

I meant to say that the water does not fill in the appliance when I shut it off. So it makes me believe that it definitely needs the pump.

The volume of the E. vessel is 18L i have attached a photo of the box which it came in.

Also I have attached the photo of the valve that was replaced and the combination valve prv setting.

Edit: the valve that was changed is picture 223137, this circled part

John.G · 19-08-2023 10:34pm

Thats fine, he replaced the whole combination valve, the PRV is set to 3.0bar which is OK IMO, the expansion vessel comes precharged to 1.9bar, I would ask the plumber if he checked this and if he pumped it to 3.0bar which, if he did, is far too high, that should be set at 1.5bar based on your pump capacity, see below.

The pump starts when the system pressure falls to 1.4bar, I don't see what stops it, normally, on this type of pump, it will continue to run as long as the demand is above a few LPM and if no demand will stop when the pressure reaches ~ 2.5bar. This pump has its own pressure vessel which should be charged to 1.4bar, he should check this as well.

When the washing machine or dishwasher are filling does the pump run continuously or is it start/stopping rapidly??, if you open a hot or cold tap does it run continuously until the the tap(s) are shut off?. Edit: I think as long as the flow is greater than 1.0 LPM then the pump should keep running and I would expect the filling flow when either one of these machines is filling is well above this.

Can you also post the capacity of the HW cylinder, its on yet another label on the side of the cylinder.

Walrus HQ200.pdf

Pump Output. LPM/Bar

11.4/2.5, 22.7/2.3, 34.0/1.9, 45.0/1.5, 57/0.96

Would expect typical pressure 2.3 to 2.5bar based on demand.

Yulkmn · 20-08-2023 6:54am

Thanks @John.G

He checked the pressure of the E cessel and then pumped it to 2.3bar and the pump to 1.8 bar i believe.

Ill post a picture of the capacity of the HW when home from work, later on.

He mentioned to me that it may be due to the washing machines solenoid valve cutting it off and the issue is due to the washing machine, can this be possible? IMO it isnt but, im not 100% sure?

John.G · 20-08-2023 7:09am

It's possible, that's why I would prefer if the EV prepressure was reduced to 1.5bar.

Anyway do check if the pump is start/stopping rapidly when either is filling.

If so open a cold tap just sufficiently to enable the pump to run continuously and then check for thumping when either filling and when sol valve shuts.

(Its OK, you've allready posted the cyl capacity, its 200L.)

Yulkmn · 20-08-2023 4:15pm

So I have just tested that, I have a cold tap running while the washing machine is on, and it doesnt make the thumping/banging noise...

Any ideas now what the issue could be and a solution , other than having the cold tap running every time i run the washing machine haha

John.G · 20-08-2023 5:09pm

Did you note if the pump runs start/stop if you are filling with no tap open? If so do another test, keep opening the cold water tap very slowly until the pump runs continuously, then run this into a container for exactly 30secs, measure this with a 1L container, X2 to give the flowrate in LPM. or just run it into a 1L milk bottle and take the time exactly in secs to fill it.😀

John.G · 22-08-2023 8:39am

I'd say you definitely have a faulty Pump flow switch as my W/machine fills at ~ 8.4LPM and my D/washer at 7.4LPM that I measured a few years ago (and found the results just now) My mains pressure was, then and is now, 3.4bar so at your fill pressure of ~ 2.5bar would expect well over 5LPM from either of your appliances.

Of course if the pump is running continuously while filling (withoiut running a cold tap) then if room allows, install two shock arrestors, one on each machine which may solve the problem.

Yulkmn · 16-09-2023 8:37pm

Hi @John.G ,

Thanks for all your feedback! Apologies with my delayed response it has been very busy the last couple of weeks around the house..

What do you mean by faulty pump flow switch? Do you mean the pump is faulty?

Is there any way of testing this? To make sure that is correct?

Currently the plumber has rerouted the plumbing and has now bypassed the pump for the w/machine and dishwasher, they now use the mains. So there is no thumping in the hot press when they are running.

However, there is a thump/bang from the cold and hot taps in the bathrooms when i close them. If i close them very slowly they do not bang. The bang can also be heard in the hotpress where the tanks are. These taps work from using the pump.

John.G · 17-09-2023 5:59am

Is this a new problem?, the original problem was only with the dish & wash machines.

Yulkmn · 18-09-2023 10:21am

I dont believe its a new problem, I think i just never noticed it up until recently. As its making the same noise/bang as dish and washing machine when closing the tap.

It seems related, when the machines close their valve it bangs, and when the taps close it bangs.. so i believe its linked to each other.

But is there any test I can do to test the pump flow switch? As the the fault light on the pump is not lighting up

Thumping noise from expansion tank

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