Unvented cylinder warped and split. Advice please!

[Rybo_1]

I'll begin from the very start. Been working at a new build 5 bed house. Lovely job to be on. First fix done soley by myself. When testing i air tested each run of pipework separately to ensure pressure was at which points I intended. So I know I have no crossed pipes. Installed boiler room 2 months ago, 2 30kw worcester Heat onlys and 2 250L worcester cylinders on pressurised heating system with a low loss header. System has been filled and heat tested ever since. Temporarily wired up and running at a low temp so I could get the UFH running for other trades and also enable me to pull hot water through at every point. Everything has worked perfectly for two months. On Friday the system was wired up by an electrician.


Today I drained off water to enable second fix of final cloakroom and this would be the last time Id be doing such a thing as all worked now valved up. Drained in my normal way of isolated cold supply to cylinders. Open highest tap, same height as cylinders, and then drain from lowest point. Did my work and went back up to refill when I saw that one of the cylinders has totally warped. Split the casing and pulled in the hot and secondary hot feeds. I was immediately alarmed about this and as I had never seen this before I called up the boss and he came out to have a look and was stumped too. All safety devices are in place. Pressure reducing valve on the incoming main at stopcock.


So we called out a worcester bosch rep and he said that I had drained system incorrectly, even when there are draining instructions still on side of cylinder. Apparently you have to crack the nut on top of cylinder which neither of us have heard of before.


I'm now worried that it could be something else and I'm reaching out for any advice on the matter


Thanks

 

[lame plumber]

makes sense to me what they say, I normally crack the prv to help drain down, even if they are vessels with exp vessels not just the air pocket variants. Dont know why, just told to do so years back, know I know why!

 

[stevetheplumber]

is it possible the tap you opened on the top floor has a non return valve on it? many of the built in mixers do

 

[emerald]

i always open a prv too, just to be sure. ive seen the result of an imploding cylinder whilst it was still half full when i was called in to replace it... they didnt want the original plumber back, it made one hell of a mess. i would be thinking myself lucky that it didnt flood the place too

 

[Best]

I was also of the idea you had opened a hot tap that has a non return valve.
I guess this is where an anti vac valve fitted at the cylinder would have stopped the cylinder imploding.
It is a lesson to us all where the unit is higher than a drain off source on a lower floor.
I have tended to open the prv, but slackening the hot outlet makes sense.
Pity the unvented course doesn't teach about those possibilities.

 

[kay-jay]

i would like to see the pics of the cylinder.
it does however sound like it has imploded.

 

[Rybo_1]

Here's a pic that I have zoomed in on when I had finished the install,

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[Rybo_1]

And the second shows how
much the cylinder pulled in

 

[Rybo_1]

 

[Rybo_1]

 

[Rybo_1]

 

[emerald]

ooo tidy pipe runs

 

[mountainman]

I reckon it was the fault of the sparky.

 

[TFGplumbing]

ooo tidy pipe runs

Offft I agree, very tidy

 

[oz-plumber]

Well Implosions are far better than explosions.

This link is not mythbusters .

Big bang sends water tank sky high | Bayside News

Homeowner capped off his leaking PTR valve because it was leaking.