In message , Bob
wrote
After being abandoned by Expert Appliance Care, who have the contract for
Whirlpool's warrenty repairs (long story [1] ), I'm left needing to repair
the water supply tube. It's a thin plastic tube, with a 4mm internal
diameter (or it is as far as I can tell).

Why not replace the whole tube?

Try Aquarium shops or garden centres selling tropical fish. The
'airline' tube that connects between the pump and airstone comes in a
4mm internal diameter size.

The same shops should have connectors to join the tube but as you say it
will reduce the internal diameter. In my experience the end of the tube
has to be softened in boiling water to get the tube fully over the
connector end. When cool the tube is securely held. In a fridge is the
join likely to become hot again?

The mini tube that is used for irrigating plants ,in hanging baskets,
also appears to have an internal 4mm diameter. Larger garden centres
will have connector for joining this type tube/pipe. Again the connector
has a reduced internal diameter. The more expensive brands (Hozelock)
have a better quality (harder) tube and the connectors screw into the
end of the tube rather than just push on over serrations on the
connector.
--
Alan