On 9 Jan, 14:58, "Grumps" wrote:
Can I repeat "Unbeliever"s request for an explanation of the
difference between tube and pipe? *Some of us here are always
interested to learn technical esoterica.

Tube; OD is the critical dimension 15mm, 22mm copper.
Pipe ID is critical 1/2", 1", 25mm, 20mm steel.
Old 1/2" imperial copper was pipe, so the OD is nearly the same as
15mm metric copper tube.