Expansion vessel failure

[danlightbulb]

Hi all,

Expansion vessel failed I think - water flows straight out the shraeder valve when depressed.

Going to give full backstory though because I need to decide how to proceed.

I moved into a new house only a month ago. The boiler was serviced back in March 2022 and as part of the house sale this service certificate is obviously something that was supplied to me - all pretty standard checks from the solicitor.

On me taking ownership of the house, first I discover that the boiler pressure gauge does not work.

So I call up the person that serviced the boiler back in March, the previous owner of the house had used him for some time (his sticker was on the boiler).

He came and had a look, then went away to order part etc. Anyway 2 weeks later (I didn't use the heating at all during this time), he came back to replace the gauge, started up the heating, said all working ok, and left.

A few hours later I notice that the pressure is up over 3 bar. I drain some off from a rad in the kitchen.

Pressure is going from <1 bar cold to >2.5 bar hot.

I read up on this, check a few online videos, and give the shrader valve a little push. Water floods out.


So:

Boiler only serviced in March 2022. I find it unlikely that the expansion vessel and pressure gauge both happen to fail in the time between this service and me taking ownership, I think there is a reasonable chance these problems already existed.

Which means I can't trust the guy that serviced it, as it wasn't identified during the service or when he came to swap the pressure gauge.


I don't know whether to give this person a chance to explain/correct the issue, or write him off and go to someone else straight away.


Boiler is a Worcester Bosch Greenstar 25Si mk4 installed in May 2013 so its only 9 years old.


Need to get this repaired obviously. What would you do?

 

[Madrab]

Probably just did a combustion check to issue a GSC, though if it was marked as a service then all that should have been checked as part of that. Could it all have just failed, well yes, highly unlikely but it could have. EV failed and it over pressurised and that broke the gauge. Given the fact that you didn't pay for it I would suggest there's not a lot you can really do.

You may have call on the seller but even then it's a little too far down the line now.

It needs a remote EV installed and as long as there is a suitable place for it to live then it should be a huge expense and you might just have to bite the bullet

 

[danlightbulb]

It needs a remote EV installed and as long as there is a suitable place for it to live then it should be a huge expense and you might just have to bite the bullet

Unfortunately there isn't a good place for it. Boiler is in the kitchen near an external corner with a window immediately to the left, flue goes up and out horizontally. Space above boiler is 320mm, below is a washing machine and the room directly above is a bathroom with no space for this either.

So its a replacement expansion vessel, which I understand due to the space limitations will require the boiler off the wall (according to manual, 340mm minimum is needed to remove the vessel without removing the boiler).

I have a few options:
* Get someone independent in to repair it - probably a few hundred quid.

* Take out one of the British Gas repair plans where they will repair the boiler for a fixed cost as long as I take out their boiler cover. I think this will cost about £250 for the year but I'm then covered for further failures as well.

* Go gold plated option and spend £2k on a brand new boiler with 10/12 year warranty, as part of this I get modern controls and a system flush.


Is a 9 year old boiler worth repairing over replacing - it doesn't feel that old to me but I don't want to sink money into it.

 

[terryplumb]

EV doesn't need to be close to the boiler.
The EV may not need replacing ,just recharging ,You need to firstly establish which.
could be a simple fix.

 

[danlightbulb]

The EV may not need replacing ,just recharging ,You need to firstly establish which.

Water is coming out the shraeder valve at the top of it. No air in it at all. I understand this to mean the rubber inside is compromised.

EV doesn't need to be close to the boiler.

There really isn't anywhere. Any heating cupboard that may have been in the bathroom has long since been removed, and the heating pipes don't go up into the loft. The rest of the heating pipes are under the floor voids.

 

[terryplumb]

Depends on how much water comes out. If you keep it open does water eventually cease ?

 

[danlightbulb]

Depends on how much water comes out. If you keep it open does water eventually cease ?

I didn't want to flood the kitchen, but it is a continuous stream yes. Its not just spluttering, there is no air at all in it.

I could try and pump air into it but the system isn't drained and Im not allowed to isolate the boiler and remove the cover to drain the boiler.

The pressure gauge is reading zero right now though, even though the system isn't drained. Its because I let more water out of a rad in the kitchen to get some air into it for a substitute air vessel. That doesn't make sense either, the boiler is 2.5-3 metres below the highest radiator so pressure should be at least 0.2-0.3 bar just from the static height of the upstairs radiators.


Had another look at possibility of external expansion vessel - its possible I could locate one directly above the kitchen window to the immediate left of the boiler, and box it in. There is about 250mm of height available there.

 

[oph]

9 years old?

Had to break it to you, but the life expectancy will be 10 -15 years max on a modern day combi.

Try isolating to cold mains water in using a bladed driver. Its a quarter turn. Leave it off overnight having drained off rhe excess and then report back

 

[danlightbulb]

@oph pretty despicable from a manufacturing point of view if true.

Can I please ask you to clarify the 2nd part of your post? You want me to isolate mains cold feed (so we won't have any hot water from the taps or shower) and then try to drain the expansion vessel (via the shraeder valve?)?

Im unsure what this is trying to achieve if you can elaborate that would be appreciated.

 

[oph]

Don't before you go to bed. Therefore no use overnight.

Re the boiler, yes and no. They arnt as reliable as they used to be but then none is your car, but I'll bet you ask a lot more of your boiler than your car.
And the boiler was a lot cheaper than your car was.

 

[danlightbulb]

Don't before you go to bed. Therefore no use overnight.

Re the boiler, yes and no. They arnt as reliable as they used to be but then none is your car, but I'll bet you ask a lot more of your boiler than your car.
And the boiler was a lot cheaper than your car was.

I don't think the cold water inlet/heat exchanger is compromised - the system pressure is not climbing over time. Is that what you are checking for?

 

[Johntheo5]

To use a rad as a temporary EV, shut both rad valves, open rad vent, slacken connectio n to rad at one end, drain off all water, retighten connection, shut rad vent, open one only rad isol valve, preferably the return , re fill system to no more than 0.75bar

 

[terryplumb]

You do not need to turn off mains cold water to work on the EV . Nor do you need to remove anything from the boiler.
What do you mean you can't isolate the boiler ??

 

[danlightbulb]

You do not need to turn off mains cold water to work on the EV . Nor do you need to remove anything from the boiler.
What do you mean you can't isolate the boiler ??

My understanding is that to properly try and recharge the EV I need to drain down the boiler, which I can't do without removing the boiler cover which I can't do because I'm not qualified.

To use a rad as a temporary EV, shut both rad valves, open rad vent, slacken connectio n to rad at one end, drain off all water, retighten connection, shut rad vent, open one only rad isol valve, preferably the return , re fill system to no more than 0.75bar

Done this, turned heating on now will see what pressure gauge reads shortly.

 

[Johntheo5]

My understanding is that to properly try and recharge the EV I need to drain down the boiler, which I can't do without removing the boiler cover which I can't do because I'm not qualified.

The boiler drain should be underneath the boiler with the gas supply, flow&return isolating valves, etc. I would be a bit wary of shuting those boiler isolating valves as they may drip on re opening them.