Hot water cylinder leak - essex flange

I've got up this morning to a leaking water cylinder.

It has done it before when the heating was turned off for a week last year whilst on holiday, yet after running again it didn't leak, so I could not find the problem.

Noticed yesterday a slight stain on ceiling below the airing cupboard, today it was worse.

Shining a torch around I can not see any leaks from the tank, although I suspect it is only leaking when cold due to contraction. I did notice that an essex flange on top of the cylinder that used to supply a shower (now disconnected and blanked off) was looking a little worse for wear, the seal is perished and breaking away, and there are tell tale signs of a leak around it.

Before I noticed this I was ready to purchase a new cylinder and just get on with it, although now it looks like the flange is the problem I'm in two minds.

I've never fitted one of these before, but understand they can be a little tricky? If I want to just blank it off, is there anything else I could use, or will I have to use an essex flange and blank the pipe coming out of it?

Any advice appreciated

Hmmm, just had another look and I'm not so sure now.

The floor under the tank is fairly wet, yet the joint around the essex flange is a little green, it's not looking particuarly wet, no obvious signs of water running down the outside of the cylinder either (don't think the water would run down the inside of the insulation as it is glued by the look of it).

Not sure how old the cylinder is, the house is a late 60's build, but not convinced it's the original one. It's a Hercal Herculag if that helps to identify it's vintage?

For the sake of £150 and piece of mind I'm tempted to replace the whole thing before it gets any worse. Is it advisable to get a new immersion at the same time?

Most likely to be the bottom seam of your cylinder leaking - its common enough.
Replace the immersion heater at the same time - its unlikely the old one would come out without a battle anyway.
John