I have a cylinder that provides the hot water for our flat. Recently,
we noticed that the overflow was dripping o some work on the ballcock
is required but on looking at the cyclinder I am unsure if we dont
also have an additional problem as physically it looks as though there
is a slight leak.
To keep things simple and safe I would like to remove the cylinder and
replace it but I am struggling to "identify" the type of cyylinder I
have. This may seem strnage but the cylinder appears to be in two
parts. THe main unit appears prety standard and contains two seperate
heater elements. Interestingly though, there is what I think is some
sort of "header" tank that sits on top of the main cylinder and
contains cold water as well as the ballcock and the overflow. This
tank is also open to the elements. The water in this tank is never
anything but cold, it is fed directly from the mains. THe cold water
suply as one would expect is direct from the rising main and both the
cold supply in bathroom and kitchen are fed from the main, not via a
tank as best as I can tell.

My question(s) firstly, what type of cylinder do I have and are
replacement cylinder easily found? (The property is approximately 15
years old). Is the "extra" tank a header tank as I assume and is it
only feeding the cylinder beneath? Is this really some form of gravity
fed system or is the main cylinder sealed and the hot water supply is
under pressure (the hot water supply presure is poor at the best of
times but all propertiues in the development seem to have this
issue??)

THanks for any help!

Jasper