The International Association of Plumbing and Mechanical Officials (IAPMO) recently published the monograph of proposed changes to the WE-Stand, which is short for Water Efficiency and Sanitation Standard. The document was previously identified as the Green Supplement.
There are four remaining state-written plumbing codes used in the United States. You could say that the remaining four states are just stubborn. Maybe they think they do it better than the model plumbing codes, but they don’t.