Unvented cylinder - advised it may explode

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BigBadBarry

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Hi - wonder if someone can give me an opinion. I am undecided whether I should pay thousands for a repair, or whether I'm just being scammed.

In short - I have a solar-powered hot water system (hot solar fluid gets piped through the inside of an unvented water cylinder). When the water from the taps isn't hot enough, my Ideal Logic boiler should kick in and top up the temperature.

That stopped happening - there was just luke-warm tap water coming out of the taps, and the boiler wasn't switching in to make it hot. (It shows "0" (standby) constantly on its display.)

Anyway, I called a plumber and he looked not at the boiler, but at the unvented cylinder in the cupboard. He noted brown, crusty build-up around where the pressure release valve (?) attaches near the top of the cylinder, which is crumbly and looks like the stuff which builds up on old batteries. He also showed me some water coming through the tundish - not masses but more than just a drip-drip. He called his boss on the phone who told him to tell me, the system wasn't safe, I shouldn't use it and we would need a new cylinder. He switched the whole system off and asked me to sign something on his phone screen to confirm he'd advised me not to use it.

10 minutes later the boss, who'd never set foot in the house, emailed me a quote for £2300.00 for a replacement cylinder and also phoned me and told me it could explode and take the roof off, and I should watch some videos of this happening to see how serious it was.

That's where I'm at - need to either get the work done, or know it's a scam and go elsewhere. Anyone got any suggestions? I can take photos of the system if it helps at all.

(Incidentally, the pressure release valve can be turned by hand, which opens the flow through the tundish, so it doesn't appear to be blocked.)

Thanks for any advice.
 
The brown stuff clearly looks like it's caused by leakage, but it's been like that for years and it's dry to the touch.

20220820_142844.jpg
 
I don’t hold my unvented qualification, but imo, it does want replacing.
 
Thanks. Why do you think it needs replacing? There is the corrosion-like area and probably a very slow leak but the brown material is on the outer surface. Looks like the grey paint is bubbling a little - (top-left of the brown part) - does that mean the whole cylinder would need to go?
 
If the PRV is doing its job then the risk of explosion is (afaik) low. I'd suggest you try another plumber in the first instance, that price (unless you're in central London) sounds a bit steep. Did yon plumber email you a copy of whatever you signed, be interesting to see it (redact business names, names, addresses etc of course)

EDIT Bubbling paint on metalwork does suggest the cylinder is eol. Is it elderly and magnetic (ie steel not stainless steel)
 
BigBadBarry said:
Thanks. Why do you think it needs replacing? There is the corrosion-like area and probably a very slow leak but the brown material is on the outer surface. Looks like the grey paint is bubbling a little - (top-left of the brown part) - does that mean the whole cylinder would need to go?
Click to expand...
It doesn’t look like it would last long, but I’ve not dealt with any unvented cylinder’s like that, so could be wrong.
 
CBW said:
10 years old according to commissioning sticker
Click to expand...
Well that's not really old. Is it magnetic?

EDIT Just looked at pics a bit closer- yeah that corrosion doesn't look good. Again don't be alarmed into spending rush job money, get another (G3) plumber in to assess situation.
 
That has been leaking for quite a while so connection on cylinder might be gubbed but its going to be a case of taking the temperature pressure relief vale out and seeing if connection falls apart if it does then new cylinder required .
No it wont explode but you may end up with serious water leak if that is left unattended .
As for 2300 for new cylinder that in my pricing structure is quite excessive for a relatively simple job to those qualified to do it
 
It should certainly be de pressurized and inspected ASAP , it probably rises to a pressure of 4/4.5bar when fully hot but expansion vessels do fail and the pressure will then rise to 6bar if a expansion valve fitted or 7bar if not and might then find a weak spot and at the very least cause ~ half its hot contents to flow around the place, not pleasant to say the least.
 
Thanks. Appreciate the feedback.

It has been playing on my mind what I 'signed' on his phone. He just said to keep the system all switched off in case it exploded, and when I said I wasn't sure I could do that, he said well, you'll have to sign something to say I advised you to. I didn't think anything of it, just thought he was covering himself, but all I saw on his phone was a white screen, which I initialled. Bit naiive of me, but I took it on good faith at the time.

Yep, the cylinder was new fit (new-build property) in 2012. Nothing but trouble with our water and solar since we moved in.

So it won't explode, I can keep using it now but get some quotes for a replacement? Quote he gave me was £1950 for a cylinder fitted, plus VAT. Solar side to be re-commissioned at my expense.

Can anyone advise - he was called out because of the initial issue with the boiler not firing up to keep the hot water "topped up" with heat at the taps. So far as I know, this is nothing to do with it. I have a £100 bill for that call-out, but he hasn't seemed to address the reason he was called - or am I mis-understanding how it operates?
 
Cylinder will probably be is duplex S/Steel and tapping should be brass so it may only be the outer casing that is rusting.

As suggested though you need to get someone UV qualified in and get that TPRV out and check the whole cylinder and safety devices. If it's just the outer casing that's rusting and the tapping and inner cylinder is all fine then it doesn't necessarrily need replaced but that'll be for the UV engineer to decide.
 
As @Madrab suggests, the Joule website says all its cylinders are stainless steel. One supplier website has suggested the cylinders come with a 25 year warranty! (Although a quick look on the Joule site couldn't confirm this)
I would be tempted to contact Joule directly and see what they say - although for the outer corrosion to get to that state, I don't know if the cylinder has been serviced according to the MI, so a warranty claim may be problematic.
 
Should be plenty of life in that cylinder yet provided the gradual leak hasn't excessively corroded the TPRV connection.

When was it last serviced? This should be done annually, to ensure the safety features are operating correctly and preserve the 25 year warranty. If it's not been done recently then this should be arranged.

I think the company you called are trying to have your pants down personally. These cylinders are under £1000 to buy and swapping like for like shouldn't take more than half a day, especially if they aren't recommissioning your solar as part of the job. Find a different G3 registered engineer to look at it
 
As Madrab says, further investigation is required.
First thing would be to unscrew the T&P valve that's leaking and see if the union is intact, the rust etc might just be a result of a small leak from that union, rest of cylinder may be perfectly ok.
Please don't pay that much for a cylinder swap if you have to change it, that quote is excessive.
 
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