Water leaking through tundish

[gaigy]

We're really confused by this problem:
We have a Tribune HE unvented system which is roughly 3 years old. A while ago we noticed cold water dripping through the tundish. We replaced the Pressure relief valve & that temporarily cured the problem. Then within a week or so, we noticed hot water dripping through the tundish. The plumber changed the valve attached to side of water tank & that also temporarily cured the problem.
However, cold water has once again started dripping through the tundish. On advice of a plumber, we were advised that the pressure expansion vessel (potable) needed replacing. We have replaced that, but water is still dripping through. It varies from a drip, to a continual stream. Our plumber advised us to keep the mains turned off (unless we needed it for short periods of time) & we've turned the boiler off so we don't have any hot water.
We've also replaced the valve from the CH expansion vessel (red one) & the valve seems okay, as well as it's pressure.
Does anyone have any other suggestions. I'm at a loss of what is causing this problem.
I'm not very clued up on plumbing so any suggestions is 'lay-mans' terms would be appreciated.
Thank you

[kevplumb]

Quote:

we were advised that the pressure expansion vessel (potable) needed replacing.

was the precharge pressure in the new one 3 bar

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[picasso]

as above or the pressure reducing valve is crackered.

[gaigy]

Thanks for your reply.

Yes it was, we got a like for like replacement & checked the pressure with a foot pump.

[kevindgas]

as piccasso says look at the pressure reducing valve (fitted to cold inlet pipe) as that is most likely failing to regulate the pressure.

A G3 unvented qualified person should be dealing with this and should have the necessary guage to check the water pressure.

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[gaigy]

Would there be something causing the valve to fail? We only replaced this about 4 - 6 weeks ago, so I guess there must be something causing them to continually fail. Would there be too much pressure in the system?

[kevindgas]

gaigy wrote:

Would there be something causing the valve to fail? We only replaced this about 4 - 6 weeks ago, so I guess there must be something causing them to continually fail. Would there be too much pressure in the system?

are you sure? there are 2 items on the cylinder 1. a reducing valve and 2. a relief valve
1. limits the pressure enteringthe cylinder
2. limits the temp and pressure already in the cylinder

the pressure reducing valve can have up to 10 bar inlet and around 3 bar outlet to the cylinder

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[gaigy]

okay - sorry, I misunderstood earlier (as I said I'm not technically minded about this, I only learnt the term 'pressure reducing valve' 6 weeks ago...)

No, we haven't replaced the 3 bar pressure reducing valve.

We've only replaced the Expansion relief valve (6 bar) & the Temp & Pressure relief valve, oh & of course the expansion vessel.

Is this a potentially hazardous situation? And are we right to keep the water turned off most of the time? Are we safe running the central heating? We've been keeping that off apart from short bursts when it gets too cold.

Thank you very much for all your assistance with this.

[gaigy]

Also, is there anyway we can test to see if it is the 3 bar pressure reducing valve that's faulty.

they've changed the part a bit from the original one which is going to require some changes to the pipework in order to get it fitted. I would hate to go to all that expense if it's not going to fix the problem.

I've uploaded a picture - just to be sure - it's the grey valve that you're suggesting needs replacement? The pipe it's on comes up from where the cold water main tap is. We've replaced the red one above it already.

[/img]

[rojaca]

Deleted. realised was talking carp

[rojaca]

Sounds like you've already changed quite a few parts unecessarily.
Without wanting to sound melodramatic the PRV and TPRV are safety devices. If either of these are dripping then you have a safety issue. As your cylinder does not have an internal baffle then i'm sure the M.I would advise you to contact a suitable qualified (unvented hot water) engineer straightaway.
Do not be misled by the fact that your cylinder is "only plumbing", the safety issues involved regarding UVHS in my opinion should be taken as seriously as those regarding gas work.

[picasso]

to answer your question, yes the grey valve is the prv and needs to be changed, also ok to use your heating but probably not a good idea to use your hot water until its fixed.

[kidgreen61]

I recently came across a similar problem to yours.

After a bit of headscratching, I realised the cause of the dripping was mains cold water passing through a mixer valve somewhere in the house.

The solution is to fit a checkvalve on the hot water outlet of your cylinder.

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[picasso]

kidgreen61 wrote:

I recently came across a similar problem to yours. After a bit of headscratching, I realised the cause of the dripping was mains cold water passing through a mixer valve somewhere in the house. The solution is to fit a checkvalve on the hot water outlet of your cylinder.

if you look at the picture you will see there is a balanced take off for the showers, so its very unlikely that unbalanced pressures are causing this problem.

[kidgreen61]

if you look at the picture you will see there is a balanced take off for the showers, so its very unlikely that unbalanced pressures are causing this problem.[/quote]

Kitchen tap?

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