Exploded expansion vessel

[Riley]

From the start I will say this is not installed by me.

I was called out last night where an expansion vessel on an unvented cylinder has rusted through and gone pop. Serious flooding etc.

Went over and made safe and I’m now trying to source replacement parts.

I note that rather than using the specific port on the combi block The installer had teed the exp vessel off the cylinder cold feed due to lack of space. Now I wouldn’t have said this would cause an issue with expansion however it obviously isn’t installed to manufacturers guidelines, can anybody else offer an opinion on this. When fixing I will obviously pipe correctly but I just wanted to know for my report if this would’ve caused the expansion vessel failure? Any thoughts much appreciated

 

[Welder]

Which side of the cold feed Riley? Before or after the control block?

 

[Riley]

After mate

 

[Riley]

In the pic the pipe off the top of the valve goes up, bends, tees and goes up to the vessel and down to the cold feed to cylinder

 

[Welder]

Ok. So long as it's on the correct side of the PRV and there is no NRV getting in the way of it doing its job, then it will work fine no matter where it's teed off.
AFAIK, there is no perfect place but in my mind putting them on the cold side is more sensible as the rubber of the bladder can be impacted by water heat.

One thing I can sat for sure however is that that control block has never been serviced. The PRV is pristine; never had a spanner put on it.

 

[Riley]

Correct Dave and that will also be going in the report. It’s a classic example of non-education again I have never been to this property however I have done lots of work for the owner before he always has boilers in other properties serviced meticulously

 

[Last Plumber]

As long as it is tee'd off after the NRV it should be fine. I tend to view those as convenience and will use them if it's easier.
Have a look in the Exp Vess. The potable water type have a bag inserted and a flange plate (normally). If the bag has perforated and the vessel is the usual mild steel, it won't take long for the wall to rust, due to the constant replacement of fresh water. How often has the customer had the installation serviced?

 

[Welder]

Correct Dave and that will also be going in the report. It’s a classic example of non-education again I have never been to this property however I have done lots of work for the owner before he always has a boilers in other properties serviced meticulously

Poor guy has suffered through simply ignorance. He can do nowt about what he knows nowt about!

 

[Last Plumber]

Just read new posts.

 

[Riley]

And thank you Dave for your thoughts it’s appreciated. You know sometimes when you’re looking at something and it just doesn’t look quite right

 

[Riley]

Poor guy has suffered through simply ignorance. He can do nowt about what he knows nowt about!

Well yes had I known he had the cylinder I of course would have advised correctly. It is an HMO for recovering drug and alcohol sufferers. As are his other properties, all from a charity but I also know that he does everything correctly and to the book normally just not this time it would seem

 

[Riley]

Just read new posts.

Hi Last, what did you mean??

 

[Welder]

As long as it is tee'd off after the NRV it should be fine. I tend to view those as convenience and will use them if it's easier.
Have a look in the Exp Vess. The potable water type have a bag inserted and a flange plate (normally). If the bag has perforated and the vessel is the usual mild steel, it won't take long for the wall to rust, due to the constant replacement of fresh water. How often has the customer had the installation serviced?

Potable vessels (as should be used here) are normally 'lined' to be classed a potable. The lining both minimises the opportunity to contaminate and extends the vessel life. Remember the bag simply sits inside the vessel so is not in its own 'space'. Unf tho most of the 'linings' are done quite cheaply and do eventually break down giving rise to this problem.

 

[Riley]

As long as it is tee'd off after the NRV it should be fine. I tend to view those as convenience and will use them if it's easier.
Have a look in the Exp Vess. The potable water type have a bag inserted and a flange plate (normally). If the bag has perforated and the vessel is the usual mild steel, it won't take long for the wall to rust, due to the constant replacement of fresh water. How often has the customer had the installation serviced?

Sorry mate I’ve read it now

 

[Welder]

Hi Last, what did you mean??

Playing 'catch up'?

 

[Riley]

That’s fine so at least I can say there is no issue with the install other than the fact it’s not been serviced regularly.

 

[Last Plumber]

Sorry for delay, yes, by time I had written, you had both moved on passed what I was saying anyway.
Happens a lot!
Maybe I should write less or write faster

 

[Welder]

Sorry for delay, yes, by time I had written, you had both moved on passed what I was saying anyway.
Happens a lot!
Maybe I should write less or write faster

Ah bless

 

[Riley]

As a follow-up on this one I just wanted a second opinion. We were obviously in agreement that the cylinder had not been serviced regularly. The owner has asked me a fair question. As the expansion vessel had rusted out and gone pop how would servicing have helped? I mean it’s true as I wouldn’t be able to see the internals of the vessel. I have made the necessary repairs today and have tested the pressure reducing valve and it was set perfectly so other than that I can’t see how we could’ve predicted that explosive ending

 

[Welder]

You couldn't have seen an explosive decompression agreed. However, when tested you'd have seen the lost of vessel pressure due to the failed bag. At that point it would have been changed so it would never have deteriorated to the point of catastrophic failure.
If it had been maintained, the flood & damage would not not have occurred.

 

[Riley]

Very true mate he isn’t questioning me he just wants to understand