Expansion Vessel leaking - Only 7 months old

5starpool

In April the expansion vessel above my boiler in the hot press started leaking and I only noticed it when the water was seeping through the floorboards in the hall. I bought a new replacement 12L expansion vessel in Heat Merchants and got a plumber to fit it for me. For a while afterwards the hot water was a bit dirty when turning on the taps until you ran the water for a while. This vessel had been installed in 2006 when the apartment was new, so lasted around 7 years.

This evening I noticed the water in the hall again, and the bloody new expansion tank is leaking again and the hot water is absolutely filthy with chunks of dirt coming out of the tap when the hot water is turned on.

This vessel is only 7 months old, so I'm assuming it shouldn't have gone again. Is there any reason why these things can fail on a regular basis and is there anything that should be done when this is replaced to essentially clean things out to ensure the hot water is clean? I don't fancy having to pay €150 every few months to replace this part.

I appreciate any help as this is certainly not my area of expertise.

Thanks.

shane0007

Is the vessel part of the heating system or the hot water cylinder? Is it red or white?

5starpool

shane0007 wrote: »

Is the vessel part of the heating system or the hot water cylinder? Is it red or white?

It's a red 12L one and sits 6-9 inches above the hot water tank in the hot press. I can take a picture of the arrangement if that will help?

shane0007

Yes do so. It sounds like you have a pressurised hw cylinder & the vessel is for that, and if so, the red vessel is the incorrect one. It must be the white ones as the continuous oxygen damages the diaphragm. Depending on the size of the cylinder, 12L sounds a bit small.

Take a pic

Stojkovic

Should have bought it in BSS instead.

5starpool

Thanks. Here is the boiler with the vessel above it.



Here is the vessel itself. The brown stain on the lower right hand side is where the water is coming out. It is a similar place I think to the leak in the previous one.

shane0007

As I suspected. Wrong vessel. You must change it for the correct vessel. Also change the location of the vessel. It should be off the cold feed to the cylinder.

D1 pipe from T & P valve also piped incorrectly.
Can't see a tundish fitted either.

For the correct pipework layout, see http://www.santon.co.uk/docs/36006153_Standard_issue_01.pdf

shane0007

Expansion vessel size for cylinder:

100L, 120L & 150L cylinders = 12L vessel
170L & 210L cylinders = 18L vessel

5starpool

Thanks for that. It is a 120l tank, so ok on that front it seems anyhow. What is the difference between the white and red tanks for interest sake? Is it dependent on whether it is pressurised or not, and that is causing the the leaks? That's what I take from what you are saying anyhow.

The pipes have been like that since install, so it's been wrong all along you say? It sounds like it would be a reasonably big job or is it not that much in reality?

shane0007

The difference is the quality of the rubber diaphragm inside the vessel. You can use the white vessel on hw or heating systems but you can only use the red vessel on heating systems as the continuous oxygenated water perishes the diaphragm of the red vessel, thus why you are seeing leaks.

For re-piping, it is best to use a certified installer who is certified in unvented cylinders or at least somebody who can read & follow manufacturer's instructions! It will depend on your piping, how pipe material was used for pipe D2 to the termination point, what diameter D2 is used & length of D1 which can be no longer than 600mm. D2 must be calculated diameter to include number of bends, etc.

I have yet to come across an unvented cylinder installation in this country that is installed 100% to regs & MI's.

5starpool

How would I go about finding someone suitable? If anyone has any suggestions I would be happy to get a PM. I am in Dublin 15. I got a quote for supplying/replacing the vessel in April of over €350 which had no mention of any pipe work and I thought it was a bit excessive, but if I can be sure that work that is needed is done to ensure it's finally done properly I'm happy to get it done right.

Thanks again for the advice.

shane0007

€350 for a new vessel is nuts money.
I cover that area but I am nuts busy at the moment. If passing I wouldn't mind popping in & giving you a few free pointers so at least you would know what should be done.

If you changed the vessel before yourself, then go to your suppliers & get the correct vessel & change. Gary71 is certified also & knows his stuff too. JohnnieK is also not far from D15 & he would be a good bet also.

JohnnieK

I have come across potable water vessels in red. The key is the data sticker on the vessel which the plumber has kindly put against the wall in this case.

Also If if it is a central heating vessel 12L vessels are only set to 1.0/1.5bar. The T&P valve would be lifting when the unit is hot.

Was the water brown before the original vessel went or is this only a recent occurrence?

freddyuk

shane0007 wrote: »

The difference is the quality of the rubber diaphragm inside the vessel. You can use the white vessel on hw or heating systems but you can only use the red vessel on heating systems as the continuous oxygenated water perishes the diaphragm of the red vessel, thus why you are seeing leaks.

For re-piping, it is best to use a certified installer who is certified in unvented cylinders or at least somebody who can read & follow manufacturer's instructions! It will depend on your piping, how pipe material was used for pipe D2 to the termination point, what diameter D2 is used & length of D1 which can be no longer than 600mm. D2 must be calculated diameter to include number of bends, etc.

I have yet to come across an unvented cylinder installation in this country that is installed 100% to regs & MI's.

Shane, If this is true it may be worth a sticky warning to all unvented system owners. How long before one goes bang? I guess this is most likely to happen in a cold winter. In the UK it is part of building reg's and needs a certificate so you cannot sell the house without the paperwork. I am sure it is a criminal offence to install a system and not have the permissions / certificates in place.
Not sure about here. Plenty of Gas warnings but no steam as far as I know.

shane0007

The issue is that the regs do not exist in Ireland for unvented cylinders, only MAnufacturer's Instructions. Therefore plumbers do not know they are making mistakes probably because they may feel odd reading a manual for installing a cylinder!

The other issue is the lack of training courses. There is only one I know of & this is in Metac, but it is rarely run due to lack of interest from plumbers. The training course is only a certification for the UK also.

Warning labels? Who would put them on, who would provide them & who would read them? Plumbers won't, manufacturer's do not understand why in Ireland there is no certification process & will not stand over any warranty in Ireland unless it is installed properly. As for reading them, if nobody bothers to read the MI's why would they read a label?

The only way things will improve in Ireland across the whole building industry is to introduce a Building Control Department. We are probably the only country in Europe that does not have one but we are probably the most likely country that needs it most!

Until then, the attitude of the installer will remain that he knows best & why would ever need to follow MI's, when he has never had a problem with the way he has been installing them for years. If the prv leaks, he just blanks it. Doesn't leak anymore after that!

freddyuk

Thanks Shane for the explanation. It knew solar PV had few regulations which seemed to go against common sense but having no controls over a potential bomb is quite amazing.
I guess the plumbing is so bad on the bodge jobs a joint will start to go before the system explodes thus giving some warning. But if that joint does not slowly fail and it suddenly gives way then boom!

By "sticky" I mean a general post at the top of the forum list not sticky labels.
At least then any consumers could check themselves for obvious missing components and call in a safety check.

JohnnieK

There are more unvented installations out there than you think in Ireland, and a good few I've come across are installed to manufacturers requirements.

The most common faults I've come across are expansion vessels on the hot outlet and t&p valve's not piped to outside just looking onto the floor :-O.

We need building control and registration big time in this country.

shane0007

The major safety concern with unvented cylinders is not pressure but rather temperature. A stainless steel cylinder is certified to 10 bar, tested to 15 bar and generally blows at circa 25 bar. It will pretty much never reach that pressure from most faults.

So, take the temperature side of things. Water boils to steam at 100C at atmospheric pressure. At 1 bar pressure, this is increased to 123C. At 2 bar it's 143C & 3 bar 174C and so on. So we think it will never reach that temperature. Solar systems are frequently in excess of 100C. High limits stats are upto 114C by regs & normally at 104C.

Take example of 300L cylinder.
1 litre of water turns to 1,600 litres of steam.
Cylinder at 2 bar pressure won't turn to steam until 143C so ok there.
Water reaches 110C but t & p valve blanked. But still ok.
Customer opens a tap & introduces atmospheric pressure bring boiling point of water from 143C to 100C.
Water is 110C.
Now 300 litres of water turns to 480,000 litres of steam. This cannot fit into a volume of 300 litres of cylinder, so.....

K.Flyer

Interesting videos on the subject...

And the Mythbusters version...

shane0007

Without sounding like a creepy stalker I'm going to be really low:cool: and rob one of Shane's oldest sayings:

shane0007 wrote: »

I have yet to come across an unvented cylinder installation in this country that is installed 100% to regs & MI's.

I investigate service/warranty issues for a cylinder manufacture and over the years i'v seen 1,000s of installs, i'v yet to see one that as Shane says meets regs or MI's, some come very close but none that would be good enough to meet UK requirements(sometimes it's a good install but no marine ply).

I find(at times)the lack of interest by a installer to read the bloody installation manual(has colour pictures for crying out loud) absolutely disgraceful.

A unvented cylinder or under sink water heater not fitted correctly can lead to explosions(very common in the UK before G3 came in) but usually they burst or the safety valve lifts flooding the property.

There is no warranty for a cylinder fitted incorrectly and home insurance will not payout on any damage caused by a incorrectly fitted cylinder. Recently a installer had to suck up a €20,000 claim against him due to a incorrect install.

Now most installer have heard of G3 and will say" what has that feckin Brit cack got to do with me" surprisingly a lot because when a claim or issue is investigated the person investigating is using G3 regs to judge a install:eek:

Now forgive the ramble:o but I do get up on my soapbox having seen more than one installation where children and the oaps are put in harms way:mad: or from the many, many times I'v had to explain to a householder they have no warranty or insurance claim from flood damage.

shane0007

I let you steal that one on me Gary

Mythbusters attempts are very good & great watching however I would prefer if they used it more accurately. All they did was build up the pressure until the cylinder blew. Where would there be a situation that the pressure could get upto 25 bar pressure. Fairly non-existent without temperature. I would have preferred if they carried out the test by heating the cylinder to above atmospheric boiling point & then opened the cylinder to show the explosion. It would have been more dramatic & more realistic.

K.Flyer

They did do another example where all the safety devices were disabled, all openings plugged and the stat by-passed and they turned on the electricity.
That was quite a dramatic one, but I cant spot the vid on you tube at the moment.

Pressure although a factor is not what's causing me problems, it's when the safety valve lifts that's when the buckets come out(and the hankys).

My advice to anybody with a unvented system is ask yourself where will the water go when the safety valve lifts?

Bearing in mind you could have very, very hot water/steam coming out of the valve where it's going is a important question, unfortunately for many when those valves lift it results in high levels of water damage or at times people get scolded(sadly) also when the valves are piped to outside they can be left pointing in directions where people can get burnt usually children:mad:

Unvented cylinders should be checked every year:eek: but who does that, the safety valves should be lifted to check them and flow of water that's released should be monitored to make sure it doesn't flood the house and terminate in a safe place.

I find a lot of installers/home owners I meet on warranty issues are complacent with unvented installs, everybody thinks these things happen to other people and it won't be them.

I was working on a boiler in Dublin, when out of the corner of my eye I spotted a unvented cylinder sitting in the kitchen, i happened to notice firstly that there was no motorised valve, ok that's not uncommon but then worse I noticed not only was there no 6bar but no T/P valve either.

I spoke to the installer who told me no valves came so he assumed they weren't important and took great exception to me getting involved in his business and suggested as someone who parents had me out of wedlock(they didn't, another assumption) would I not think about retuning to London at my earliest convenience. Now I did think of putting the boiler on max and strapping myself to his cylinder but it was only 200 Lt. and I'm a big boy.