H-e-l-p! Leaking unvented HW cylinder

[Ericthelobster]

Have just discovered that my sealed (ie mains-pressure) HW cylinder (a 7-year-old Vaillant Vantage 200L) has developed a slow leak. Now, as I'm not qualified to work on unvented systems I'm obviously not about to attept a repair myself, but would like to narrow down the problem a bit before I call in a pro, as this could clearly be hugely expensive to resolve.

The tank seems to sit within a snugly-fitted, grey plastic dish about 1" high (see photo in link below), and this dish is full of water and overflowing, and I can't see where the leak is. However, removing the immersion heater cover reveals a spongy seal (see photo), which is sodden, especially below the element. Now AFAICS the best case scenario is that the seal on the flange around the immersion heater has gone, which would be relatively straightforward to sort out; however I'm wondering whether it's possible that the wet sponge has just sucked up water by capillary action from the grey dish below?

http://img.photoamp.com/i/Sf3AQ2RDd.JPG

I don't know anything about the anatomy of the tank inside its outer metal casing, and I wonder if anyone who does might be able to comment on the likely cause of the leak?

 

[clf-gas]

That "spongy seal" is the insullation. my rekoning is the seal for the immersion boss has failed (large bolted plate). Get a G3 guy in as recommisioning will be required after repair.

 

[Ericthelobster]

That "spongy seal" is the insullation. my rekoning is the seal for the immersion boss has failed (large bolted plate). Get a G3 guy in as recommisioning will be required after repair.

Thanks, I'm hoping that's what it is. Do you know what sort of seal it is - an O-ring or something? I'm thinking the best thing might be just to buy one so when the engineer comes he can complete the job there and then, if that's what the problem is.

Presumably it will be pretty obvious when the boss is unbolted whether that's the source of the leak (and don't worry, I'm not about to try!) Is there anything else I can do to confirm?

Thanks

 

[ChrisR]

Looks like yours is slightly older , but the bits are on the pic:
http://www.partsarena.net/gas/catalogs/vaillant/System/DATA/DS2/71/2271F.htm

Link may show a blank for you but it is there, honest.
Start at
http://www.partsarena.net/gas/catalogs/

 

[chrishutt]

starting with the second link that ChrisR gave, follow Vaillant - Storage Water heaters - VIH Vantage 200/3 1995-99 - boiler section. The flange joint is shown.

 

[Ericthelobster]

Having continued my investigations, I've found a tiny puddle on top of the tank, and discovered that the leak is from (what I think is?) a pressure regulation valve:
http://img.photoamp.com/i/WhwIxxwXs.JPG
I hadn't noticed it before; but it's hidden away behind the thermostat housing and under a low shelf in the airing cupboard... anyway, evidently the leaked water is finding its way inside the outer casing of the tank on top, running down inside it and then exiting at the bottom - which did kind of wrong foot me.

So... this looks a whole lot more straightforward to sort out. Does this device simply need unscrewing and replacing or is it serviceable? Again, not intending to do it myself, just trying to keep it down to a single service call by having in the appropriate components.

Thanks

 

[giblets]

That looks like the main pressure reducing valve. I don't know if they can be repaired so probably a replacement job.