General plumbing regulations, code administration, permits, and inspections
Scope and authority
This domain tests code administration, not pipe fitting: who may perform work, when a permit is required, which drawings are reviewed, and which inspections release the project. The adopted plumbing code, local amendments, and the authority having jurisdiction (AHJ) control. A permit is normally required for new construction, alterations, replacements, and additions to drainage, water, gas, or vent systems; ordinary minor repairs may be exempt only if the adopted code says so. The permit application identifies the owner, contractor, scope, valuation, and fixtures. Plans must show riser diagrams, fixture units, pipe sizes, venting, and water-heater details when required.
Inspections and closeout
Typical inspection holds are underground or below-slab, rough-in before concealment, and final after fixtures and testing. Tests may include water or air pressure for supply, water test for drainage, and smoke or air test for vents. Concealment without approval is a common violation. A final inspection verifies fixtures, backflow protection, labeling, access, and corrections. The certificate of occupancy or final approval is not a substitute for contractor licensing, bonding, and insurance.
Worked example
A homeowner adds a basement bathroom. The plumber submits a permit with a riser diagram showing a 3 in. building drain, a 2 in. lavatory and vent branch, and a new water closet. The AHJ requires a below-slab inspection before concrete, a rough-in inspection before drywall, and a final. The plumber schedules the underground inspection after setting the closet flange and before pouring, the rough-in after pressure-testing water and water-testing drain, and the final after trim-out. If the plumber skips rough-in, the final cannot legally close the concealment.
Traps
Assuming a fixture swap never needs a permit; starting before permit issuance; missing local amendments; treating an inspection as a courtesy rather than an approval hold; failing to keep approved plans onsite.