symptoms of a faulty pressure vessel

[Ralphmalph]

Can anyone tell me what the symptoms would be with a faulty pressure vessel in a combi system?

 

[Shaunthegas]

Getting to high pressure quickly and PRV blowing is a good indicator

 

[warrington]

If you have water mixed in vessel. If water coming out when you press the air hole it is faulty.

 

[Ralphmalph]

would there be an indication of that by looking at the pressure needle

 

[warrington]

you can't really tell from pressure needle, if the pressure needle drops yes it is one of the signs that expansion vessel is faulty but at the same time there may be leak somewhere that causing pressure loss.

 

[warrington]

and when the system works you can see the rise on the pressure gauge.

 

[arran197]

If you run the heating (not the hot water) and make sure it gets nice and hot, the pressure gauge will rise up to a higher than normal level, such as 3 bar until the prv discharges. If this is the case then further investigation needs to be done. If you press the valve at the top then some water may come out. But the best thing to do is drain the boiler and test it with a pressure gauge ( like you would test the tyre pressure on your van). If it's low on pressure (they're usually around 1 bar) then you can try re-pressurising it. This might solve the problem. But going back to water coming out the valve, this will need a new vessel.

 

[dontknowitall]

An expansion vessel full of water is a heck of a lot heavier than one half full. Sounds a little obvious but then some of these problems are!

 

[Ralphmalph]

thanks for replies.I'm not sure now as my pressure is 1 at cold then about 1 and 3/4 when hot which seems normal.
when heating first comes on i can hear a quick gurgle of water which sounds like air going through the pipes.Also when hot water interupts heating, at the end of that cycle you can hear a quick gurgle of water and sometimes hear air coming out of AAV.After a week of this i have to bleed the upstairs rads.Thought it might have been expansion vessel.

 

[CES]

Sounds like you have air in the system.

 

[arran197]

You can't check the vessel pressure when the system is full of water. You need to drain the boiler. But if it's hot and the pressure gauge is still at 1 and 3/4 bar then I would say that's ok. If you need to keep bleed the rads then I would be looking at a leak somewhere which is dragging air in. But, if one of the rads is only half full of water, this can also act as an expansion vessel. The air in the rad taking up the expansion.

 

[SimonJohns]

Just give it a tap. If it sounds hollow its ok. If its dense. It's broken