Leaking Fortic Cylinder

[CANDYPANDY]

Ok,
I have the above named water storage cylinder up in the loft space. My father seems to think it is the Fortic type -me I have not the foggiest.
The problem is that over the last 4 or 5months it has been leaking -drops of water coming through the ceiling on the stairs landing directly below .
Here is some more detail for the knowledgeable ,this only happens when the central heating system is set to supply hot water.It does not appear to occur when central heating is set to provide CH only.
I have been up in the loft space and verified this is the source of the dripping water -the cylinder is covered with an insulating jacket and I have little confidence in myself to locate the exact source of this leak.
My goal at the moment is to identify the exact position of this leak with your assistance and then apply some of the magic spray that is supposed to stop any leak guaranteed.
thanks for any help

 

[leakydave]

If the cylinder itself is leaking you more than likely need to replace it. If it is a Connectio to the cylinder it can more than likely be repaired.