Plumbing code varies by municipality, so a legal install in one city fails inspection 10 miles away

The U.S. has two competing model plumbing codes (International Plumbing Code and Uniform Plumbing Code), but municipalities can adopt either one, modify it with local amendments, or write their own. A plumber working in suburban Chicago might operate under different trap arm lengths, vent sizing rules, and backflow prevention requirements than a plumber 10 miles away in a neighboring jurisdiction. The people who suffer are plumbing contractors working across multiple municipalities -- especially in metro areas where a single day's jobs might span 3-4 jurisdictions. A legal rough-in in City A fails inspection in City B, costing the plumber a re-work trip ($200-400 in labor), a re-inspection fee ($75-150), and a day or more of schedule delay. This persists because plumbing code adoption is a local government prerogative with no federal mandate for uniformity. Local amendments often exist to address genuine regional differences (water quality, seismic zones, freeze depth), but many are legacy rules that no one has revisited in decades. Each municipality's building department is a separate bureaucratic fiefdom.