Expansion vessel checking

[jordy_boy]

Hi everyone,
Put the central heating on for the first time and noticed the pressure kept rising from around 0.5bar to about 2.5 at which point I switched it off. Its gone back down as its cooled so I thought I'd check the expansion vessel valve to see if it needs recharging. However when pressing the pin in the middle of the valve water squirts out.
Is this a definite sign the vessel needs replacing??

The boiler is a vokera unica 28he.

Many thanks

 

[Jajodu]

i would say so, the diaphragm has split.

 

[jordy_boy]

I thought so unfortunately thanks for the reply.

I've heard a cheaper and quicker option is to fit an external one? But I was trying to see where he could fit it and am struggling to find somewhere appropriate. There is a bit of space down the side of the boiler but the external vessels seem to take up a lot more room. Is that right? I was looking at an 8l one which I believe is what my boiler currently has and they are around 400mm x 275mm dia! That seems huge to me

 

[ollski]

It's not proof it's failed. There can easily be a glassful of water in the air side from condensation. Drain the pressure and leave the drain point open as you pump up the vessel. If you end up with 1bar of air in the vessel and 0 in the boiler then shut the drain and repressurise the system and see how you get on.

 

[jordy_boy]

Oh really? OK I will give that a try. There is one of those fernox filters fitted down the side of the boiler can I just use that as a drain point?
Thanks again for your help

 

[mcmoby69]

The FAQS cover this issue.

 

[jordy_boy]

In FAQ tho it says if water come out valve vessel needs replacing??

 

[andytw]

If it looks like it is a keeper then change the valve. If it has been wet then it will be rusty and probably not seal.
Usually just a screw in schraeder tyre valve insert from Halfords.

 

[gasbusters]

When charging it stick to about 0.75mbar.

Water squirting out may not necessarily mean its finished. Usually, but not always.

 

[jordy_boy]

Just an update. I pushed the the pin in the shraeder valve to get the rest of the water out which wasn't too much more. the boiler pressure was still over 0.5 bar and no air or water was coming out, if it had failed wouldn't water be coming out until the pressure was zero?

I then drained system till pressure was 0 and tried to pump 0.8 bar in with an electric pump but the pressure just seemed to quickly drop each time. I put some fairy on the valve to see if it was leaking but didn't seem to be.

So I presumed the vessel needs changing.
But I've refilled the system and had heating on the last 2 days and pressure seems to be fine?? Is this likely to be short lived?

I've got a plumber coming Tuesday to have a look anyway just wondered what you thought? Thanks