Unvented cylinder problems - over pressure or faulty expansion tank?

[MrJack2021]

Hi,
New to this forum and also complete novice who knows pretty much nothing about plumbing.
However I have done quite some google searching trying to find some answers.
I live in a 1st floor flat which uses an electric duel element direct unvented water heater cylinder (150 litres).
Recently I noticed a small leak somewhere on the copper pipe with the pressure relief valve and tundish. But I think its been leaking for some time because there is green corrosion and scale all down the copper pipe, and also lots around where the valve outlet connects to the tundish.
I have also seen a lot of water running through the tundish in the mornings when the waters being heated, which according to my searches, means either the pressure valve is faulty (which going by the corrosion I mentioned, could be?), or there is actually too much pressure perhaps because of a faulty expansion tank.
The pressure valve red cap says rated for 7 bar, is this normal? All mentions I could see of such devices were around 2-3 bar.
Currently got a bucket under where the drips are forming, collecting about 2 inches a day.

 

[Deleted member 120897]

You’ll need to engage with a G3 registered engineer to repair that and probably needs a service, it could be a few things.

 

[king of pipes]

You will need a service call that expansion vessel looks as though it's not supported at all when these fail they are really heavy and will cause problems if not secured , the pressure relief will need changing and all other safety devices need checking . Kop

 

[Pete the heat]

Your system has lost its expansion capability. The problem is due to the expansion vessel having lost its air charge and results from either an air leak to atmosphere or a failed diaphragm.
You would need to depressurise the hot water system by shutting off the cold feed and then opening a hot tap. If the expansion vessel is healthy then water should come out of the tap for quite a few seconds before stopping. If it 'dies' straight away this is a sign of the expansion vessel being full of water due to losing its charge. Most vessels have a simple tyre type valve/connector under the plastic cover and with the system depressurised there should be an internal pressure of say 1 Barg. This can be checked using a tyre pressure gauge. If there is no residual pressure to unit is faulty. Quickest solution go the plumbers merchant and buy a new one. set the pressure to 1.0 Barg using a tyre pump and refill your system the mains water pressure will do the rest.

 

[townfanjon]

Hi,
New to this forum and also complete novice who knows pretty much nothing about plumbing.
However I have done quite some google searching trying to find some answers.
I live in a 1st floor flat which uses an electric duel element direct unvented water heater cylinder (150 litres).
Recently I noticed a small leak somewhere on the copper pipe with the pressure relief valve and tundish. But I think its been leaking for some time because there is green corrosion and scale all down the copper pipe, and also lots around where the valve outlet connects to the tundish.
I have also seen a lot of water running through the tundish in the mornings when the waters being heated, which according to my searches, means either the pressure valve is faulty (which going by the corrosion I mentioned, could be?), or there is actually too much pressure perhaps because of a faulty expansion tank.
The pressure valve red cap says rated for 7 bar, is this normal? All mentions I could see of such devices were around 2-3 bar.
Currently got a bucket under where the drips are forming, collecting about 2 inches a day.

Ignore the post from Pete above ^^^^^^ hes guessing. You need an experienced G3 man .

 

[king of pipes]

Your system has lost its expansion capability. The problem is due to the expansion vessel having lost its air charge and results from either an air leak to atmosphere or a failed diaphragm.
You would need to depressurise the hot water system by shutting off the cold feed and then opening a hot tap. If the expansion vessel is healthy then water should come out of the tap for quite a few seconds before stopping. If it 'dies' straight away this is a sign of the expansion vessel being full of water due to losing its charge. Most vessels have a simple tyre type valve/connector under the plastic cover and with the system depressurised there should be an internal pressure of say 1 Barg. This can be checked using a tyre pressure gauge. If there is no residual pressure to unit is faulty. Quickest solution go the plumbers merchant and buy a new one. set the pressure to 1.0 Barg using a tyre pump and refill your system the mains water pressure will do the rest.

This is not strictly true Pete your giving the advice for a heating expansion vessel that is set at 0.7 - 1 bar ? . A potable expansion vessel is not something a DIYer should be changing it needs replacing and supporting correctly and should be fitted with a flow through valve the new vessel is set at 0.2 below the incoming water supply pressure this avoids water hammer , contamination and protects against legionnaires disease , the cylinders combination valve filter will need cleaning and the safety devices checked and replaced if found to be faulty again this is not something a homeowner should be attempting , these problems are normally due to the lack of maintenance and servicing and the COVID epidemic has seen people leave important safety checks, as a consequence their systems are failing and are costly to repair or replace. Regards kop