Draining system - replace radiator

[Jupiter01]

Here’s a picture of my boiler arrangement.



There is a megaflo to the right of this picture and I believe that I have a system boiler.

I know a bit more…

I have a multizone underfloor heating system downstairs (Manifold downstairs) and a separate zone upstairs. I believe that in that picture we can see two sets of flow and return. Each with their own diverter valves. The flow and return going up to the loft feed all the upstairs radiators. They drop down to each radiator.

Problem - none of the rads have a drain cock and not sure how much it would help anyway, with a drop down system?

I now need to replace this bathroom rad.




This is not too far from the shower tray in the bath.

Can I please get some advice on how to approach this.

I have previously drained a combi system but the rads had a drain cock. There are some differences here that are causing me some concern.

Thanks in advance.

 

[terryplumb]

Are you replacing rad like for like, same size?
Unless you want to change the valves and/ or ammend pipework ,there is no need to drain the system.

 

[ianmcd]

Each with their own diverter valves

They are not diverter valves, they are zone valves, not the same thing,as @terryplumb advised if you are keeping the same valves,and not altering the pipework no need to drain anything