Expansion Vessel Placement Advice

[Deleted member 97000]

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.

 

[ShaunCorbs]

Any pics of the water heater ?

 

[Deleted member 97000]

Any pics of the water heater ?

Sure. Forgot to upload actually.

I didn't do the plumbing

 

[Harvest Fields]

I didn't do the plumbing [/QUOTE]

On that note I’m out.

 

[Rob Foster]

View attachment 35537
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.

This maybe your gaff and may be abroad but working on unvented stuff is illegal in uk and nuts if you are not certificated , they can and do go bang , your insurance is invalid and your family and neighbours at risk. I am fully experienced ex gas corgi, acops, acts hetas and had all the tickets inc the ones to manage installers , I would not do unvented as I am not trained or up to date Rob Foster aka centralheatking

 

[Riley]

Think you need a pro mate

 

[Deleted member 97000]

Sorry I probably should have mentioned this is NOT gas. The water heater runs on electricity.

 

[Riley]

I don’t think that was the concern it’s that it’s an unvented pressurised device which can go off like a bomb if not installed to Manufacturers instructions. You must be qualified to work on them so by your logic it’s as in the Uk so you can’t work on it

 

[snowhead]

I'd guess this is Bulgaria?
Unvented cylinder installations and incidents take no account of borders and need suitably qualified people to work on them.
If it doesn't have an expansion vessel it definitely needs one.

 

[Deleted member 97000]

I'd guess this is Bulgaria?
Unvented cylinder installations and incidents take no account of borders and need suitably qualified people to work on them.
If it doesn't have an expansion vessel it definitely needs one.

Sadly there are no 'pros' in BG. If they don't see leaks as a problem, then they definitely won't see an unvented/ sealed cylinder installation with no expansion vessel as a problem either. In all the villages and towns, they're ALL sealed.
The reason I believed this could be a tackled by an experienced DIYer is because I've seen numerous videos on youtube by professional plumbers (Plumber parts) demonstrating how this is carried out. Surely he/ they wouldn't be demonstrating how to achieve a successful installation to professionals??

So... I have to make do with taps breaking all the time due to a problem I can't resolve?

In that case, if anyone fancies a holiday with free food and board in return for fitting an expansion vessel, let me know!