Welcome JimBob:
It is nice to have another Plumber on the Forum. Much of our plumbing history came from the UK (like Sir Thomas Crapper) and our orginization "Plumbing Heating, Cooling Contractors" uses an apprentice text book written by a former Britt.
My answers are based on the Kentucky Plumbing Code and will vary with other codes at times; its not a professional jelousy thing, its just the code I have lived with and taught to many others.
Glenn