I have a 32mm Alkathene incoming water main, reduced at internal
stopcock to a 22mm copper riser.

This is all inside my (attached) garage - so inside the property.

Thinking of adding a 22mm tap on this copper riser ..... 2 fold use ...
to allow water in the garage when required.
Plus to allow a full flow water feed to be used on a hose (to outside
the house)
I do have a 15m outside tap .... but thinking of a higher flow.

So it is an 'inside tap' not an external tap.

I would put a Tee on the 22mm rise feed this to a 22mm full flow balofix
type isolation valve, then to the 22mm tap.

If it were an external tap then I would fit a double check valve .....
is there any requirement for a check valve on this 'internal' tap.

Obviously you could connect a garden hose to any internal tap - these
would not have a check valve - but as this is slightly different
installation (not a bath or sink) ... just wondering what water by-laws
apply.