Zilmet 300lts Expansion vessel - air leak - faulty weld?

[john999uk]

Hi, I have a 300lt (yes its about 5ft high, 2ft wide) expansion vessel that assists in maintaining our cold water pressure during high demands (3 story 5 showers). It has been working well over the last few years but recently the air pressure has dropped. I have found the leak, it is the top flange, looks like 2 washers tack welded on outer vessel to increase strength. Looking at it it looks like it was not welded correctly at manufacture.


Any idea if it can be repaired or is it a right off?

Thanks for any help you can give.

 

[lame plumber]

might be wrong but my understanding of accumalators is they use a rubber balloon to build up pressure and if that goes its knaclered, so your leak is a symptom of a failed rubber balloon - knackered vessel

 

[Roger Welton]

I agree, some vessels have replaceable diaphragms, from what I can see of the pic you have posted, it looks like you are going to have to replace the lot.

 

[john999uk]

Thanks for the replies. Yes it does use a rubber balloon but it that ruptures then, dependant on pressure you get water coming out of the schrader valve or air out of the tap closest to the accumulator. The Zilmet Ultra pro does indeed contain a replaceable 'balloon' but unfortunately it looks like its that actual steel pressure vessel that has failed.
I might have to remove the 'balloon' and then get the flange welded then reinstall.

Just for info a new expansion vessel is about £500 and a new 'balloon' is about £300.
For info the water is contained inside the 'balloon' and the air is between the balloon and the inside of the pressure vessel. So they can be used on potable water. The balloon has a flange about 300mm on bottom with 1 1/2inch pipe thread on and a 1/2inch at top that can also be connected to showers etc.

Thanks for your help.

 

[lame plumber]

we knew that, we thought you didnt 🙂

 

[Chalked]

Couldn't you remove the ballon and get a fabricator to weld the leak?

 

[IDCHAPPY]

Sounds like you'd be as quick replacing it?

 

[john999uk]

we knew that, we thought you didnt 🙂

😀 I am not a plumber, but I do have engineering experience in other fields. I always like to be able to understand a problem before getting the pro's in to do the work. I find it helps me avoid cowboys 😀
Thanks very much for your help.

 

[john999uk]

Couldn't you remove the ballon and get a fabricator to weld the leak?

Must admit that's what I am thinking. Although I don't know how easy it will be to find a welder who is willing to work on it as it is a pressure vessel, even though it is only rated at 10bar!

Thanks for the reply, at least I am thinking same repair method as a pro.

 

[Chalked]

Just a thought. Are the two washers there to clamp the ballon? If so could it be split between there?

 

[john999uk]

Sounds like you'd be as quick replacing it?

Maybe as quick, but if it can be welded I can uninstall and reinstall it myself. It's just the fun of carrying it down 3 flights and back once it's welded that I am not looking forward to 😀 So it's only my time which is cheap/free 🙂

 

[john999uk]

Just a thought. Are the two washers there to clamp the ballon? If so could it be split between there?

From what I can see in manufacturers installation and balloon replacement instructions the 2 washers are just there to add a bit of strength where the 1/2inch pipe passes through the vessel. The balloon has a 300m open flange at one end, the top end has the 1/2 inch pipe which is bonded into the balloon and the 1/2inch pipe does clamp between the inside and the outside of the pressure vessel.

Must admit more I think about it the more I think it needs welding.

Thanks very much everyone.

 

[john999uk]

The vessel is broken.

It's a faulty weld or corrosion

Replacing the diaphragm is not going to help

The air around the diaphragm needs to be pressurised too

Contact your supplier and get them to help you

I think you are correct, it's a faulty weld. I doubt corrosion as the 'balloon' (I wont call it a diaphram as it's not like a small pressure vessel where it has a membrane half way up) keeps the water from the steel and the 'balloon' is in tact as no water from schrader valve when opened.

I am waiting a response from UK agents/manufacturers.
Thanks

 

[john999uk]

While waiting for UK Agent/manufacturers response I have been thinking (I know it's dangerous 😀)
Looking at the 'balloon' it is sausage shaped with a 300mm ish flange at bottom and a 1/2 pipe at top. I believe this 1/2 pipe has a flange on it that the butyl balloon is bonded to. This 1/2 pipe flange is used to clamp from the inside of the pressure vessel to the outside though the 2 washers. This 1/2 pipe is clamped by a nut on the outside of pressure vessel.

I am not great at explaining this but I believe that where it appears the weld is leaking it may be cured by taking out the balloon and adding a rubber washer to the 1/2 pipe that is then on the inside of the pressure vessel and will be compressed by tightening up the external nut.

Am I being stupid?

Cheers

 

[chris watkins]

Have you tried tightening up the nut? just give it a nip-up & see if it stops. I replace one of these a long time ago & the bladder, I seem to remember, formed the seal at the top. (the 1/2"was not a water connection)
BTW if you are thinking of changing the bladder you will get absolutely black from the rubber & you better not be planing to re-pressurize it with a hand /foot pump!!!!

 

[john999uk]

Have you tried tightening up the nut? just give it a nip-up & see if it stops. I replace one of these a long time ago & the bladder, I seem to remember, formed the seal at the top. (the 1/2"was not a water connection)
BTW if you are thinking of changing the bladder you will get absolutely black from the rubber & you better not be planing to re-pressurize it with a hand /foot pump!!!!

Cheers, I have tried nipping up the nut but I can't get it any tighter even with decent spanner.

I think you are right that the bladder (been trying to work out what to call it) does form the seal at top. I believe the top 1/2" is only water connection when vessel over 100lts. Mine is 300lts so it is water, which did surprise plumber when he installed it but that's another story 😀

I might try and remove bladder and fit a gasket to inside if I can find one that will fit over a 1/2" pipe! Provided I can get one the manufacturer approves of.

I have used a little 12v tyre compressor powered from a jump start pack. Although even that takes about 90 mins (including compressor rest periods) to get 30psi in it.

Thanks again for everyones help.

 

[chris watkins]

Much better & quicker with a bottle of Oxy free Nitrogen!!!!

 

[john999uk]

So your going to try and fix the cylinder and void your warranty?
Just replace it. You won't repair it and if you do. It probably won't be right
These are also subject to PSSR and if you play with it you may find your home insurance viod

Thanks for the advice. As far as I can tell their is no warranty. I am waiting for the manufacturer to advise me on the way forward. But I am trying to understand what has actually failed.
My guess is that the bladder seal at the top has failed. It may be possible to just replace the bladder seal if there is one but it maybe a new bladder is required. I will ensure that what ever the fix is it is authorised by the manufacturer.

Thanks for remind me of the PSSR. The unit is not in a public area and we have no employees but you are right a pressure vessel should not be modified without manufacturers approval.

 

[lame plumber]

bugger employees, I worry more what could happen to family when things go wrong

 

[Ermintrude]

It's rated for 10bar but operates normally at 3.5bar. Have you pressurised and sprayed with ldf?

Bit of airline grade paste and large Ptfe or nitrile washer. If it's not covered of course! Test it statically for 5 days at operating plus

 

[john999uk]

bugger employees, I worry more what could happen to family when things go wrong

True but it's in a locked cupboard with FD30 door and only I have key.

 

[john999uk]

It's rated for 10bar but operates normally at 3.5bar. Have you pressurised and sprayed with ldf?

Bit of airline grade paste and large Ptfe or nitrile washer. If it's not covered of course! Test it statically for 5 days at operating plus

Yes ldf showed the air leak. I originally thought it was a faulty weld but after lots of research I fine the tack welds are just to hold strengthening in place.

Any washer/gasket that is required would be internal to the pressure vessel. I can statically test at double working pressure for a week or 2 as it's not in use at moment. Just doing winter maintenance and found problem.

Thanks, hopefully manufacturer comes back with replacement washer part number.