Expansion Vessel Placement Advice

[BGRenovations]

Plumbing Schematics

• BGRenovations
• 18 Nov 2018

Hi,
I intend to install an EV (expansion vessel) to my cold water line as I'm having problems with pressure affecting my water heater and taps. When the water gets really hot, the safety relief valve is triggered and drips. I never understood why this happened until it occurred to me that this is an unvented system with no EV present, therefore no means for expansion. I have never fitted one of these before so I just wanted to check whether I'm installing at the correct place on the line. To demonstrate, I have provided a PNG image to show the layout of my plumbing lines and fittings etc.

Some things I'm not sure about:

Why is the EV installed on the cold line (before water heater) and not the hot (after water heater)? I always assumed that the EV would be installed to take up the expansion of the resulting hot water, not cold prior to it being heated. If someone could explain, that would be appreciated.

Although I've got the PRV (pressure reducing valve so that we're clear) at the cold in at mains, I assume I must install a secondary at the hot out from water heater (as shown) due to raise in pressure after water heated?

Is the check valve in the right place near the EV? Do I just use a simple Tee to incorporate it to the cold line as shown? Or is there a special fitting I would need instead/ additionally?

Lastly, my water heater has a capacity of 80L and I'm unsure of what size EV to buy. Ideally I'd want to use the smallest size possible so I'm thinking a 5L or if I could get away with an even lower capacity please let me know.

So does my diagram look fairly accurate? Basically my work would consist of: teeing off for the EV and putting check valve before the tee (not after otherwise water wouldn't be able to back siphon into the EV if I'm right in assuming) and fitting PRV after water heater if necessary. Please note, Y filters not shown but would be installed.
I'm aiming to maintain 60 PSI pressure throughout to prevent damage to fittings.
Many thanks for any advice
Please note, this is a Bulgarian installation, but the procedure should be identical to UK practices.

 

[BGRenovations]

Forgot to show water heater:

DSC_1541

• BGRenovations
• 19 Nov 2018

DSC_1542

• BGRenovations
• 19 Nov 2018

DSC_1545

• BGRenovations
• 19 Nov 2018

 

[Gasguru]

No one sensible will give you advice on unvented cyclinders other than to suggest you consult with a qualified plumber that's licenced to work on them.
Of course Bulgarian water regulations are likely to be lacking and do they even licence plumbers?.
I suspect most plumbing is therefore diy....take a look a UK building regs section G3 and the manuals from UK based unvented cylinders. At least you're then on the road to a safe installation.
What does the cylinder installation manual say? I can't see a temperature/pressure safety valve towards the top of the cylinder...that's always a safety requirement here.

 

[BGRenovations]

No one sensible will give you advice on unvented cyclinders other than to suggest you consult with a qualified plumber that's licenced to work on them.
Of course Bulgarian water regulations are likely to be lacking and do they even licence plumbers?.
I suspect most plumbing is therefore diy....take a look a UK building regs section G3 and the manuals from UK based unvented cylinders. At least you're then on the road to a safe installation.
What does the cylinder installation manual say? I can't see a temperature/pressure safety valve towards the top of the cylinder...that's always a safety requirement here.

Hi Gasguru, many thanks for your reply. The water byelaws are very likely to not be as stringent as UK standards. Whilst there may be 'plumbers' (I'll use that term loosely) in the city, there certainly aren't any available where I am and chances of them commuting to a village are extremely unlikely.

I have been under the impression that such work can be carried out by a competent DIYer, hence the various articles I've read
https://www.thespruce.com/water-heater-expansion-tank-information-2719063
and videos I've watched (plumber parts).

If you look again at the last picture on my previous post, there is a safety relief valve (what the village plumber cow boy fitted with protruding horse hair and was still leaking around the thread!). Notice the green lever? That's the relief valve. But I replaced this boiler with a newer Bosch and did all the work myself. Sadly I don't have pics. I also installed a new pressure relief valve with PTFE.
All if most plumbing in BG is carried out by the home owner, probably because a lot of people can't afford to hire.
What could possibly be the worst case scenario of an ill fitted expansion tank (10L)? I've heard that they can practically explode if not installed correctly? Surely a 10L tank fitted alongside an 80L water heater is not going to cause that much of a risk? Are they really that unsafe? I can't understand why there are claims that these can be fitted by a DIYer, yet forum users (elsewhere) are claiming that it's too risky and dangerous?

 

[Elkato531]

Lots of videos on you tube of unvented cylinders exploding. They are safe if fitted with the correct safety devices and plumbed correctly. As Gasguru has said, this is not the place to give chapter and verse as its not a diy job in this country. The correct info isn't difficult to find though.

 

[Madrab]

If an unvented hot water heater thermostat fails and the water heats to over 100degC and the safety features fail and the vessel exceeds it's design pressure then worst case .... yes it can explode.

Worst Case scenario from an unvented cylinder -

 

[BGRenovations]

If an unvented hot water heater thermostat fails and the water heats to over 100degC and the safety features fail and the vessel exceeds it's design pressure then worst case .... yes it can explode.

So I can't lose then. Although irrelevant to the topic, the cylinder could explode whether with an expansion tank or without so I can't see how a vessel could cause further problems. I know my cylinder is fitted with a relief and is working fine as I test often.
I don't know how the topic has deviated to unvented cylinders when I asked whether an expansion vessel could explode.

 

[Gasguru]

Listen VERY carefully.
In the worst case scenario when the cylinder explodes you loose your house and your life.
The Bulgarian government doesn't value life the same as our government in the UK...hence they don't care about diy installations and are happy with poor plumbing standards.
Read the installation manuals for UK destined cylinders. We do not rely on just a single expansion valve...we also have another safety valve set to discharge on excess pressure or temperature. The principle of safety is to have multiple systems to provide plenty of redundancy should one device fail to operate.
Your proposed diagram has multiple faults..a little knowledge is a dangerous thing etc.

 

[BGRenovations]

Listen VERY carefully.
In the worst case scenario when the cylinder explodes you loose your house and your life.
The Bulgarian government doesn't value life the same as our government in the UK...hence they don't care about diy installations and are happy with poor plumbing standards.
Read the installation manuals for UK destined cylinders. We do not rely on just a single expansion valve...we also have another safety valve set to discharge on excess pressure or temperature. The principle of safety is to have multiple systems to provide plenty of redundancy should one device fail to operate.
Your proposed diagram has multiple faults..a little knowledge is a dangerous thing etc.

Gasguru, I appreciate your input and I hope you don't feel as though I'm trying to undermine what you're telling me; I'm simply just trying to share my views. Besides, it could be invaluable to other readers also which is a plus. The water heaters in BG are very basic. It's literally a cold feed in, hot feed out with a safety relief on the cold in which is imperative to have installed as we know in the event that the thermostat fails and as a means (but by far not very practical) escape for excess expanded water. There is a little dial to control temperature and an LED if you're lucky. There are no bells and whistles like here in the UK. That's as basic as an £80 heater gets. There's not a lot of pipework involved either as shown on the schematic. The water lines serve the ground floor only and the ceilings are all solid 12" concrete.

I've been looking again and yes there are flaws which I've just worked out with the help of myself:
No isolating valves between the WH & the EV & safety valve.
pressure reducing valve on the cold in not hot out.
This is simply the sort of info I'm in need of otherwise I'm not going to make much progress

But i know for sure that I can fit one of those little expansion vessels myself on such a simple system. Obviously I wouldn't attempt in the UK and lets face it why would anyone when you can just call a plumber out?

 

[Gasguru]

You might want to check if there's an overheat thermostat in series with the element.
If I lived there I'd be fitting a cylinder with UK spec safety.

 

[BGRenovations]

You might want to check if there's an overheat thermostat in series with the element.
If I lived there I'd be fitting a cylinder with UK spec safety.

Yes I believe so as I recall from the manual provided.
You can only buy what's available though. However, it's Bosch, so it should be pretty decent.
Oh well, pity I didn't really get anywhere, but thanks for sharing your thoughts gasguru. I appreciate your time. Thank you

 

[endecotp]

I don't know how the topic has deviated to unvented cylinders when I asked whether an expansion vessel could explode.

What you have IS an unvented cylinder.

Have you found the manufacturer’s instructions for the cylinder? They are normally available online.

I’m not certain that I’ve understood what you’re saying in these quotes so I’ll try to be unambiguous:

pressure reducing valve on the cold in not hot out.

It’s correct to have the pressure reducing valve on the cold inlet to the cylinder. This is to protect the cylinder from too-high pressure on the cold mains.

no isolating valve between the water heater and the safety valve

It’s correct to have no isolating valve between the water heater and the safety (pressure relief) valve. (If you did have a valve there you could close it, and then the cylinder would explode rather than vent through the pressure relief valve!)

there are flaws which I've just worked out with the help of myself:

Beware of overconfidence!

P.S. I an not a plumber, let alone one with the right paperwork to work on unvented cylinders!
But if you really are in Bulgaria with no competent plumbers available, I think we should try to at least make sure you don’t make your system any more dangerus than it already is!

 

[dilalio]

This is simply the sort of info I'm in need of otherwise I'm not going to make much progress

@BGRenovations whilst your plight and frustrations are completely understandable, there are forum rules regarding giving advice on this subject.

Many individuals have been held accountable and even prosecuted for what they have posted on social media.

Giving advice to you here, that you could follow in Bulgaria, could (and probably would) be followed by others, here in the UK. That, could lead to repercussions in the future for the person providing the advice and the evidence would be stored on here for all to see.

In your position, I would be contacting Bosch's technical support and explaining the situation so that they may assist.
Failing that, you would have to continue your search for a qualified engineer and pay whatever it costs to get him on site.
Or you could put yourself through a G3 course over here.
Or you could just proceed as you wish, with your alterations.

I can say that there are under-counter water heaters of around 15 litres that can use feed pipework for expansion, although an EV is a better provision. Then you have UV cylinders of XX litres which require safety devices for both cold mains pressure, coming into the cylinder, and temperature and pressure relief, within the cylinder, where the heating process commences. Where the former becomes the latter (above) is pretty much down to the manufacturers R&D and should be detailed in their instructions as to which safety devices are required.

 

[BGRenovations]

@BGRenovations whilst your plight and frustrations are completely understandable, there are forum rules regarding giving advice on this subject.

Many individuals have been held accountable and even prosecuted for what they have posted on social media.

Giving advice to you here, that you could follow in Bulgaria, could (and probably would) be followed by others, here in the UK. That, could lead to repercussions in the future for the person providing the advice and the evidence would be stored on here for all to see.

In your position, I would be contacting Bosch's technical support and explaining the situation so that they may assist.
Failing that, you would have to continue your search for a qualified engineer and pay whatever it costs to get him on site.
Or you could put yourself through a G3 course over here.
Or you could just proceed as you wish, with your alterations.

I can say that there are under-counter water heaters of around 15 litres that can use feed pipework for expansion, although an EV is a better provision. Then you have UV cylinders of XX litres which require safety devices for both cold mains pressure, coming into the cylinder, and temperature and pressure relief, within the cylinder, where the heating process commences. Where the former becomes the latter (above) is pretty much down to the manufacturers R&D and should be detailed in their instructions as to which safety devices are required.

Thank you Dilalio (and everyone else).
I have been thinking I'll probably do the right thing and consult a professional where available. I was never aware of the possible dangers of incorrectly installed unvented cylinders. Therefore, I feel it would be wise not to attempt any work on the installation (despite the lack of legal requirements in BG) apart from common minor repairs as appropriate. It's not easy to find such tradesmen in Bulgaria due to the fact they tend to work in a limited radius and are reluctant to stray from that radius and even if one is found, it's a risk whether their work is on par with UK standards. I've seen a lot of work in commercial environments which leaves me very little faith in their pride and workmanship. Ideally, I would prefer an English tradesman who could visit in spring when warm (with travel expenses paid) for however long necessary but it may not be so easy to find somebody. For the time being I may get in touch with Bosch as suggested and see what they can offer me.
Many thanks again.

 

[ianmcd]

Im sure if it was in the summer you would get someone to come over from here and sort everything for you, as you say ask Bosch who they would recommend for your area