Unvented cylinder overflow

[bunters1976]

We have a hot water tank with the overflow going outside.

Ive noticed the ground outside is always wet. I then realised the water is coming from the hot water tank over flow. Its not constant but clearly happens regularly.

Our heating is topped up from the small tank in the loft.

The hot water is pressurised via the expansion tank. This appears to be mains fed as there is no larger tank in the loft.

Any ideas what is causing this?

Any help of advice would be much appreciated.

 

[Dan Robinson]

Cylinder needs a service and that vessel shouldn't be orientated horizontally and could be guffed.

 

[ianmcd]

probably the expansion vessel needing re-pressurised or replaced and it shouldnt be installed horizontally, snap @Dan Robinson over typing each other

 

[Mike the Boilerman]

Cylinder needs a service and that vessel shouldn't be orientated horizontally and could be guffed.

That's interesting. I've noticed they are nearly always fitted vertically but what is the mechanism that 'guffs' them if they are fitted horizontally? I've never noticed an instruction to fit them vertically in the MI, but then I rarely fit them, preferring MegaFLOs.

 

[Dan Robinson]

The membrane sags against the vessel wall and eventually tears.

Many have a V or the word "vertical" on their data Badge rather than an explicit instruction.

 

[Dan Robinson]

It's similar to why square vessels inside boilers are schit.