In an earlier contribution to this discussion,
Mark Trueman wrote:

Dont know what happenned to that ascii art. Suppose thats what you get
posting through google groups

Yes, it's not easy to convey a clear picture with it!

Any chance you could stick a photo of your cylinder and its pipework on a
website somewhere, and post a link to it?

Is there room to extend the upper coil connection horizontally, to make room
for the valve but also to allow the vent to connect at the same level?

Does your boiler have an overheat cutout stat? If so, you may get away with
putting the valve in the return pipe on the boiler side of the feed pipe.
[There are others with more expertise than me on this - hopefully they will
chip in].
--
Cheers,
Set Square
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