Pressure Vessel

[pbpeter]

I have a central heating system which is a sealed system using a boiler located in the loft and a separate 8 lite pressure vessel (situated just below the boiler, resting across 2 joists) and a 3 bar safety release valve (situated just above the boiler). There are 14 radiators over 2 floors and a hot water cylinder via a diverter valve. The system has previously run at about 1/1/5 bar quite successfully.

The system is losing water pressure, when hot through the safety valve which I have recently replaced. There are no obvious leaks - certainly for anywhere near the amount of water I am having to replace.

I'm pretty sure the problem is the pressure vessel and am willing to replace it to resolve the problem. Is 8 litres big enough, and is it just a matter of buying a new one and connecting it to the same piece of pipework? I could shorten the pipe quite easily if needed due to a larger vessel.

 

[LeedsPlumber]

Yes you can change it like for like 8lt should be ok, have you tried pumping it up with a bicycle pump?

 

[pbpeter]

Thanks for that. No, I've not tried pumping it, as I don't know how I could do that. The only connection is the 15mm at the top to the system.

 

[LeedsPlumber]

Pump up the expansion vessel not the system, the expansion vessel should have a what looks like a car tyre dust cap or a big round piece of plastic take it off and pump it up.

 

[pbpeter]

I can't locate the dust cap, although the vessel is against the wall. By take it off, are you suggesting it's within the water connection?

(sorry to be thick - if it helps, it is a Flexcon vessel)

 

[LeedsPlumber]

Its hard to explain without knowing which way the vessel is but at the opposite side of the vessel to where the water connection goes in put your hand on it and you will be able to feel either a large plastic cap or a small dust cap like on your car tyre remove it and thats where you connect your bicycle pump to. Post a pic and il have a better idea.

 

[mag525]

Hello Pbpeter,
If the pressure vessel Is at fault, then as leedsplumber said, It may just be a question of re-pressurising. If the diaphram in the expansion vessel has ruptured, then a new expansion vessel will be required.
Any chance of a picture, they speak a thousand words !!, or so they say!.
Plus the fact that I am interested In why you may have an exposed expansion vessel In a domestic house.

 

[pbpeter]

Thanks for your help, I have learnt a lot today. I decided to remove the vessel and found the plastic disc underneath, and the air input under that. It refuses to take any air whatsoever, so I am resigned to a new one in the morning.

 

[pbpeter]

As requested here is a photo of the installation in the loft on the gable end wall.

Boiler

• pbpeter
• 15 Jan 2009
• 1