Gledhill light unvented cylinder imploded

[Rakesh]

First things first are you G3 qualified?

Hi,
I’ve just been searching for G3 qualification.
First thing that came up on the search was Gledhill g3 corse. 1 day £90 to become G3 qualified??
I would do the course just to have that qualification.

 

[Tim S]

The installation has been incorrectly installed and should not be used

 

[SimonG]

Incorrect installation, tell customer to contact the manufacturer for their take on it.

 

[Brambles]

If you can persuade the Client, I would get Gledhill out to view and comment on the installation / collapsed tank.

Whilst you don’t need to be G3 qualified to change washers et al on a pressurised system, you really do need to understand the principles of how the system operates and the importance of venting when draining it down.

Often these things are not clear cut.

Personally, I don’t think that the G3 course covers sufficient detail about the process and need to avoid the creation if a vacuum in an unvented cylinder. It is very easy to do this unintentionally when draining down an unvented system when the tank is at or near the highest point of the installation. Draining off bellow the tank with the cold water supply isolated has the potential to create a vaccum in the vessel. I suspect this is part of the problem here - or did you ensure that the tank could freely vent either from the prv or preferably by slackening the hot water draw off connection.

Think of the tank like a crisp packet - it takes a hard blow to burst it, but only a very gentle suck to collapse it.

 

[Welder]

Incorrect installation, tell customer to contact the manufacturer for their take on it.

100% agree. However! This needs to be done by the customer. The reason for that is if you do it then you become kind of 'tainted' by association and the customer needs to understand you are stood alongside them rather than doing it for them - hope that makes sense?

Def def def get them in. Once that's done then the customer can call the last installer back to correct it. Even if the last installer simply replicated what was there, they still have a duty of care to do the job properly. Obviously, if they were not G3 then that's yet another issue.

My advice? Stay 'close', help, but not too much.

Let us know how you get on.

PS. The course is well worth doing, BUT prepare to spend the rest of your life learning what's NOT taught

 

[oz-plumber]

Reality Rakesh,
Dislike me for all you want. I've had a few!!!

You're the last person on the job, and your work caused the cylinder to implode.
Get a report from the Manufacturer and so on, the customer will be without hot water for weeks while you wait for a resolution.

I feel the customer is not going to back you up, when waiting weeks for an insurance provided hot water system replacement.

The customer will want hot water and you're the bloke they are going to pursue to get it.

As said, I hope you have insurance

Have a nice day!!!!!!

 

[Brambles]

Yes, Dave, you are correct in the process to follow.

The reason I referred to Gledhill, or indeed any accredited independent was, that I think that the guy who replaced the washers is at risk of being blamed for the failure.

I regard high level (particularly attic) unvented installations as being “riskier” than the norm when they are not in their operational state.

If the cold water inlet to the tank is incorrectly installed and not being fed through some form of non return valve ( I cannot see from the picture how the tank is fed). When draining the cold water system, if all the hot taps are turned off and if you isolate the cold water at the house stopcock and open the cold kitchen tap, you will pull a vacuum in the tank equivalent to around a 3m head of water (assuming the tank is in the attic if a two storey house). That will be released once it can be balanced by a freely venting hot water tap ( ie no nrv). However, the hot water tap, when opened will also pull a vacuum, that will be released once it can be overcome by the cold water “pull”. If the hot tap has an nrv on it, then the position then the pull will continue to increase. This is probably why when he thought the system was empty, the hot water suddenly flowed. At that point the vacuum had almost certainly bbbeen broken by the tank collapsing.

This is quite important, because without this evidence, the initial conclusion could be that the system was drained incorrectly.

 

[Rakesh]

If you can persuade the Client, I would get Gledhill out to view and comment on the installation / collapsed tank.

Whilst you don’t need to be G3 qualified to change washers et al on a pressurised system, you really do need to understand the principles of how the system operates and the importance of venting when draining it down.

Often these things are not clear cut.

Personally, I don’t think that the G3 course covers sufficient detail about the process and need to avoid the creation if a vacuum in an unvented cylinder. It is very easy to do this unintentionally when draining down an unvented system when the tank is at or near the highest point of the installation. Draining off bellow the tank with the cold water supply isolated has the potential to create a vaccum in the vessel. I suspect this is part of the problem here - or did you ensure that the tank could freely vent either from the prv or preferably by slackening the hot water draw off connection.

Think of the tank like a crisp packet - it takes a hard blow to burst it, but only a very gentle suck to collapse it.

Hi,
Thanks for the reply.
The first thing I did was to read the manual on draining down the system. Yes as you mentioned, negative pressure created in a cylinder can cause it to Implode, however on a call I made to Heatrea sadia technical support, I’d gone through the exact step by step process of drain down, changing taps and filling back up.
The technical guy responded by saying that there was no way of imploding the cylinder with the steps I’d taken.
The cylinder would need 15 bar of negative pressure to explode or implode.
Now as you’ve mentioned, I looked up on drain down of said cylinder and sure enough there is a drain down procedure.
No, I did not drain down as per instructions, so yes, working on any of the plumbing involving the drain down of the cylinder is my responsibility and liability.
Anyone who works on any dwelling is liable regardless. There should be a proper understanding of any system installation to work on it safely.
Now I have been on this forum for some time and admittedly use it to learn of other people’s experiences.
Knowledge and experience is key, so i would like to think that I don’t undertake any work without prior knowledge.
In this instance, I admit to not knowing or researching proper drain down procedure of the installation so the only way is for me to understand what I have done or what has caused the cylinder to implode. Not only this one but also the previous one.

I’ve been installing bathrooms for the last 15 years and am proud of every single installation without any major failings. Yes the odd leak in joints and fittings but not a major failure like this.
Every day we learn something new or old but I learn something every day and never have I claimed to know everything.

Anyway, back to why you’ve rightfully mentioned....... correct drain down procedure!
I’ve taken an image of the manual and have also discussed this with couple of heating engineers, one of which I know who’s installed this cylinder.
They both admit to not knowing this drain down procedure.

All I’m doing is waiting for Gledhill to get back to the plumbing merchant I use and document everything for the client to take up with the installer.

Thant you all for your input and sharing your knowledge to point out the possible faults.
I really appreciate the input

 

[Rakesh]

Reality Rakesh,
Dislike me for all you want. I've had a few!!!

You're the last person on the job, and your work caused the cylinder to implode.
Get a report from the Manufacturer and so on, the customer will be without hot water for weeks while you wait for a resolution.

I feel the customer is not going to back you up, when waiting weeks for an insurance provided hot water system replacement.

The customer will want hot water and you're the bloke they are going to pursue to get it.

As said, I hope you have insurance

Have a nice day!!!!!!

Hi Oz,
I don’t deny any wrong doing.
Fortunately, I have discussed all my findings with the help of this forum and have advised the client of the possibility that the cylinder is incorrectly installed.
I’ve also shown him the paragraph relating to drain down procedure to show that while I didn’t carry out the procedure, I have called technical support of a different manufacturer to find if what I have done by changing the taps and draining down exactly as I did would cause the cylinder to implode.
As Mentioned, it would take 15bar of negative pressure to implode a tank so I am doing everything to come to a resolution.
If I have to pay for a new tank and install it then I will do it.
The client is being understanding and thanked me for investigating the matter.
He has been let down by two installers first one of which incorrectly installed it and second installer just changed the tank for an identical one without changing or checking that it was correctly installed in the first place.
The installer has also been serving the cylinder since the install so if what’s been mentioned here is correct then the installer has no clue on what he’s doing.
I would say if the installation is incorrect then the liability lies with the installer.
If I’m proved to be in the wrong then I will correct it.

 

[Scott_D]

Those instructions are for a full cylinder drain which im guessing wasnt needed to change a tap?