Replacing hot Water Expansion Tank - Tribune HE

[maverick100]

I need to replace the expansion tank on the hot water side of heating system. The cylnder is a Tribune HE. Clearly I need to turn off the cold water feed however I note that there is a drain tap at the bottom of the cold water inlet pipe going into the cyclinder. Do I need to drain the tank completely before removing the expansion tank?

Thanks in advance.

 

[Plumber90]

You need to be qualified to work on an unvented system for a start, and going by the fact you need to ask how to drain down, I'm going to say your not.