On 29/10/2020 14:12, 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.

'Emergency Plumber on Christmas Day Connectors'?

That's what happened to a former colleague, the punched-out copper disc
got jammed somewhere and they couldn't turn the water off. Mind you, it
was probably 35 years ago and they may have improved. The fittings, not
the family.

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Cheers
Clive