Expansion vessel full of water

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WhoMe?

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Hi

Sorry for another expansion vessel question but I can find this asked previously

Had my boiler service yesterday and the engineer said it is full of water and it needs to be drained. He didn't mention anything about having popped. I pressed the valve and zero water came out. I replaced the vessel last year.

If I understood him correctly it's filled with water because it's too small for the size of the system. The service engineer last year also said it was too small but it was the old vessel then.

Am I right in saying that the best thing to do is empty the water in the meantime and get a plumber to fit a second vessel? I'm tempted to try myself but might play it safe. Do I empty the vessel by just partially undoing the metal hose (sure it has a propper name) and let it slowly drain out, will there be a lot of pressure behind that water? Can I just turn the boiler off or do I drain it first? I'll obviously recharge it afterwards.

The boiler is a grant vortex pro 36

Thanks
 
WhoMe? said:
Am I right in saying that the best thing to do is empty the water in the meantime and get a plumber to fit a second vessel? I'm tempted to try myself but might play it safe. Do I empty the vessel by just partially undoing the metal hose (sure it has a propper name) and let it slowly drain out, will there be a lot of pressure behind that water? Can I just turn the boiler off or do I drain it first? I'll obviously recharge it afterwards.
Click to expand...

Inside the EV, is a flexible diaphragm. Intended to have water on one side, air under pressure on the other - the two kept apart by the diaphragm. Idea is, it allow the water in your system to expand, as it heats up, by pushing against the diaphragm, and compressing the air in the air side. The air side pressure is topped up via a car tyre type valve, using a car tyre type pump.

If the EV fails, the diaphragm leaks and allows water into the air side, so you get water coming out of the air valve - is that what is happening?
 
No, no water coming out but it's very heavy with water. Water drops slightly over a few days and the engineer said it's because the EV is full of water. Sounded to me that there's too much water in there that can't push out by itself. I could be wrong
 
WhoMe? said:
No, no water coming out but it's very heavy with water. Water drops slightly over a few days and the engineer said it's because the EV is full of water. Sounded to me that there's too much water in there that can't push out by itself. I could be wrong
Click to expand...

In that case, it simply needs the pressure in the EV to be pumped up, no water = nowt wrong with it. How simple can it be, are you sure he is a plumber, it's fairly basic stuff, checking and pumping up an EV?

If the EV is low is air pressure, then the water will have no where to expand into, when it gets hot. The result is that the Pressure Release Valve will open at around 3bar, to release the excess pressure. The PRV, will probably connected to a short bit of bit of pipe, which pokes out through an outside wall, likely behind the boiler. On the outside, there will be an elbow, pipe, then a second elbow pointing back at the wall - this is so that any sudden release of hot water, runs down the wall, rather than hitting a passer- by in the face.

The way to check is water is escaping via the PRV, is to simply fasten a sandwich bag over the end. If if fills, your PRV is releasing water.

There, you probably know more than your 'plumber' now..
 
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Harry Bloomfield said:
In that case, it simply needs the pressure in the EV to be pumped up, no water = nowt wrong with it. How simple can it be, are you sure he is a plumber, it's fairly basic stuff, checking and pumping up an EV?
Click to expand...
He was from Certas. Said his tools were robbed from his van and had no pump to pump up again. Said I should try calling H/O to get another engineer out

Harry Bloomfield said:
The way to check is water is escaping via the PRV, is to simply fasten a sandwich bag over the end. If if fills, your PRV is releasing water
Click to expand...
Its an external boiler and the condensing pipe/drain is all sealed and connected to an outside drain. Will this be the same drain for the prv? I'll see if there's a easy place to disconnect.

If I need to drain water is it simply, boiler off, release air from the EV and slowly undo metal hose and upside down it?

Thanks a lot for your help
 
WhoMe? said:
e was from Certas. Said his tools were robbed from his van and had no pump to pump up again. Said I should try calling H/O to get another engineer out
Click to expand...

Then how can he expect to manage to do a service, without the proper tools. Ring H/O and tell them you want the service you have paid for, done and done properly.
WhoMe? said:
Its an external boiler and the condensing pipe/drain is all sealed and connected to an outside drain. Will this be the same drain for the prv? I'll see if there's a easy place to disconnect.
Click to expand...

No, the PRV pipe should act as a 'tell tale'. It should not be regularly releasing pressure, if in fact it is.

WhoMe? said:
If I need to drain water is it simply, boiler off, release air from the EV and slowly undo metal hose and upside down it?
Click to expand...

No, there is absolutely no point in your doing that - the EV pressure needs to be topped up, and all your issues will disappear. Get them back, to do the service properly.

What you could do, if you have a bike pump, is release the water pressure by bleeding it out from a radiator, then pump air into the EV, upto 1.5bar, then top your water pressure back up - but you should not need to be doing any of that, you have paid for a service.
 
Thank you Harry, I will call them on Monday. The guy said empty the water from the EV directly but it seems that's not needed.

I'll have a search for another pipe outlet, tomorrow

CBW said:
Wouldn’t have thought an extra expansion vessel would achieve much, other than take up expansion from the one that is now flat.
Click to expand...
Strange, maybe my house looks bigger from the outside. This engineer said the EV filled up because it's not big enough.

Ta
 
WhoMe? said:
This engineer said the EV filled up because it's not big enough.
Click to expand...
If you have expansion issues with a charged (pumped up) expansion vessel, then additional one might be needed, but as yours is flat, this is why it’s full of water as when the water is heated, it has nowhere to expand to. When you pump up an expansion vessel, you expel the water via an open connection, often at the boiler or a low drain off on the heating system.
 
WhoMe? said:
The guy said empty the water from the EV directly but it seems that's not needed
Click to expand...

Re-charging the vessel will force the water out of the vessel, as long as the system pressure has been released and a vent/drain is left open as the vessel is being charged up.

Any EV, whether it's large or not will fill up with water anyway when the system heats up and the water expands, that's the way it works. When the system is cold and under normal pressure, ~1bar, then the pre-charge pressure in the vessel pushes the water out of the EV and into the system, as the system runs and heats up the water expands, the pressure increases and forces water up into the vessel, as the air can be compressed, then it does absorbing that increase in pressure and stops the system from overpressurising.

If the EV is undersized, it means that the system water volume and pressure increase is greater than the vessel can absorb, the system pressure then rises to the point that the PRV may lift.

As suggested though, they should be doing it - oh and the EV pre-charge won't need to be up as high as 1.5 bar, no more than 1bar would normally be required.
 
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