On 27/08/2020 13:10, Stephen wrote:
Thank you, that's reassuring. So if the 10mm microbore is not too
narrow, I assume I can also use a "standard" isolating valve and
don't need to use a full bore one.

What is the advantage of using a flexible hose? I was thinking the
heat might make it perish and leak? I thought boiler
manufacturers usually recommend copper pipes only within a metre
of the boiler?

There's no continous flow. You could use the type of 2mm or so OD
capilliary tube used for some types of thermometer or thermostat!