The forum sponsor is based in Seattle, WA. I believe he works under the UPC.
I and a few others are in California. The California Plumbing Code is based on the UPC with a lot of ifs/ands/buts.
We have a number of people from the East coast operating under the IPC, and folks from NYC and MASS, which both have their own unique codes.
We are aware that the answer to any particular question may not be exact, depending on code, and often that will be pointed out to the person asking the question. There are usually enough people posting that if the poster tells us where he is, someone will know his code.
Very good question, and look forward to hearing from you as often as you care to chime in!