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Google "Popcorn's Still" for all you need to know about making Likor.
For us in US 22mm is 3/4" and 15mm is 1/2" CTS (Copper Tube Size) and do not use galvanized or Black Iron as "reducing socket" use Stainless Steel fittings. All threaded pipe has same designation in US as UK, they only call the copper in mm because of EU. And make sure your stand off fittings are brass, copper or SS or you will get galvanic reaction.