Expansion vessel failure

[danlightbulb]

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.

On my boiler the drain is inside the cover, and Im not supposed to remove the cover because it has seals as part of the combustion safety system.

On the outside of the boiler on the heating pipework, there is a drain valve, but this would drain down the whole system.

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

Boiler has been on for half an hour now and system is up to temp. Started at approx 0.75 bar the gauge now reads approx 1.25. So that trick with the radiator seems to have helped.



I am leaning towards this British Gas repair option: https://www.britishgas.co.uk/home-services/boilers-and-heating/boiler-and-heating-repair.html

It will mean a £75 initial cost of the repair including parts, then a £15 per month boiler cover scheme for a year. Total cost over a year £255 which seems good value considering the repair alone will probably be more than that. Plus then I get protection from any more failures.

 

[terryplumb]

Yes it will, but it's not a long term solution.
You can use any drain point ,leaving it open ,whilst pressurising the EV.
A fair few litres of water will be expelled so it's a good idea to run a hose to drainage from the drain cock. You would need a pump with a gauge to pressurise the EV to around 1 bar.

 

[danlightbulb]

Yes it will, but it's not a long term solution.
You can use any drain point ,leaving it open ,whilst pressurising the EV.
A fair few litres of water will be expelled so it's a good idea to run a hose to drainage from the drain cock. You would need a pump with a gauge to pressurise the EV to around 1 bar.

Is there any point me trying this Terry? Its clear the EV is full of water so the rubber membrane must have failed. If I pressurise it, its a temp fix if it holds but its likely to lose pressure and fill up with water again isn't it?

 

[terryplumb]

You have not conclusively proved the membrane is perforated.
Trying to recharge The EV will prove it one way or the other. If you can't pressurise it ,it's knackered.
If you can your sorted and haven't spent much ,if anything.

 

[jeff the gasman]

You may also have a faulty secondary heat exchanger if the pressure rises overnight. Also a faulty filling loop.
Get it diagnosed by a third party engineer.
The guy who did the safety check only did a safety check. If you didn’t employ that person you have no recourse with them.
Just get it sorted to save a lot of stress or take it up with the sellers solicitor.
###it happens!
Seems a simple fix to me!

 

[danlightbulb]

You have not conclusively proved the membrane is perforated.
Trying to recharge The EV will prove it one way or the other. If you can't pressurise it ,it's knackered.
If you can your sorted and haven't spent much ,if anything.

If the membrane isn't perforated, how is the EV full of water?

You may also have a faulty secondary heat exchanger if the pressure rises overnight. Also a faulty filling loop.

The pressure hasn't been rising since Ive been monitoring it.

Filling loop is not present normally, its a key insert system to bridge the filling port.

The guy who did the safety check only did a safety check. If you didn’t employ that person you have no recourse with them.

Yeah it was actually a service - according to the paperwork anyway. But agreed, I have no comeback other than moaning at him which I can't be bothered with, I will just chalk it up and go elsewhere.

 

[terryplumb]

You do not know if the EV is FULL of water on the air side ,only that water is present.
I have told you what to do to ascertain if it's unserviceable or not, if you don't want to bother to try thats fine ,join BGas scheme,buy a new boiler,or engage an engineer.

 

[danlightbulb]

You do not know if the EV is FULL of water on the air side ,only that water is present.
I have told you what to do to ascertain if it's unserviceable or not, if you don't want to bother to try thats fine ,join BGas scheme,buy a new boiler,or engage an engineer.

Terry i appreciate the help you've given but the EV is full of water. The Schrader valve is at the very top of the EV, and when I pressed the valve it shot a continuous stream of water out. If there was air in it, it would have risen to the top and hissed out first.

It's not that I don't want to bother, but if I connect a hose to drain tap without isolating boiler it will drain my whole system out.

 

[terryplumb]

Ok , choices .......................................£ 255 to BGas.
£ 2oo/ 300 private engineer.
£ 2000 (estimate )new boiler.
Versus....
Drain water to see if EV is servicable,which MAY ( or may not) save you all of the above.
Don't get me wrong it may well be shot ,but it's possible it's not.
It's a bit of a no brainer.

 

[Johntheo5]

You have not conclusively proved the membrane is perforated.
Trying to recharge The EV will prove it one way or the other. If you can't pressurise it ,it's knackered.
If you can your sorted and haven't spent much ,if anything.

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.

Can't you drain down the system and install a EV yourself preferably connected to the boiler return, if you say how many rads, can suggest EV size, even though you can't oversize a EV you want one that is adequatel sized bearing in mind where it might be installed. You can use the original filling point.

 

[danlightbulb]

Ok , choices .......................................£ 255 to BGas.
£ 2oo/ 300 private engineer.
£ 2000 (estimate )new boiler.
Versus....
Drain water to see if EV is servicable,which MAY ( or may not) save you all of the above.
Don't get me wrong it may well be shot ,but it's possible it's not.
It's a bit of a no brainer.

Ok I'll see if I can give it a go soon. Let me just clarify what I'm looking for then when I try this...

If I can't pump up the vessel at all then the air I'm putting in is simply dissipating through the rubber membrane - vessel is shot.

If I pump it up but it won't hold pressure for very long - vessel is shot.

If I pump it up, but after some time running my boiler the pressures start to spike again when hot, vessel is shot?

I'm still struggling to see how the EV has got full of water if there isn't an existing perforation though Terry. I can't figure that one out.

Can't you drain down the system and install a EV yourself preferably connected to the boiler return, if you say how many rads, can suggest EV size, even though you can't oversize a EV you want one that is adequatel sized bearing in mind where it might be installed. You can use the original filling point.

See pictures below. The only place I could put it is up near the ceiling next to the boiler above the window. Easy access to heating return pipework but not a great location from a visual perspective and I would have to box it in.

 

[Johntheo5]

You could buy one of the mushroom type that are installed in gas/oil boilers, a bit more expensive but neater when boxed in?.
Don't know your system capacity but even a 8L EV with pre & fill pressures of 1.0/1.5bar will be sufficient for a 85L system without the final (hot) pressure exceeding 2.2/2.3bar and a 10L will be sufficient for 100L system.
Any time that I have to occasionally renew a TRV or whatever I isolate all the rads and the drain down is then minimal.

 

[danlightbulb]

Don't know your system capacity but even a 8L EV with pre & fill pressures of 1.0/1.5bar will be sufficient for a 85L system without the final (hot) pressure exceeding 2.2/2.3bar and a 10L will be sufficient for 100L system

8 reasonably sized radiators, most doubles a couple are singles, 1 towel rad in bathroom.

 

[Johntheo5]

Probably a 10L then but look up your boiler spec and see what size EV is installed, if your boiler final pressure wasn't, exceeding 2.5bar then the same sized external one.

Would recommend one of these as well as you will never have drain down the system for EV servicing/renewal.

 

[Lower]

You can get condensation building up in the air side of the expansion vessel over time that gets in there when its pumped up. If the air in the air side has leaked out so that the air gap has gone, its possible that its only the condensation that's left in the air side that you're seeing come out of the valve.

Personally, i think its unlikely in my opinion, but possible. If its a significant volume of water coming out then it's probably just a failed expansion vessel.

I'm still struggling to see how the EV has got full of water if there isn't an existing perforation though Terry. I can't figure that one out.