In message , at
00:00:05 on Fri, 30 Oct 2020, John J remarked:
On Thursday, 29 October 2020 at 14:15:14 UTC, Roland Perry wrote:
Struggling to find the keywords to guide me to buy online those plumbing
gadgets which clamp on the outside of, and pierce through, existing
pipework to attach a dishwasher feed or something similar.

Forget it - turn the water off while you work and use a compression tee
type washmac valve. Clean the pipe well before fitting.

I'm going to be fitting it to the central heating plumbing (as a drain
cock), so the concept you imply of "turning the water off" doesn't
apply.

There's a special place in hell for plumbers who install a central
heating system without a drain cock.
--
Roland Perry