Installation, Repair, Testing, and Inspection
The inspection sequence
Work runs permit, rough-in inspection, cover inspection, then final. Rough-in covers pipe in the ground and walls before concealment; cover inspection covers the materials placed over concealed work; final verifies that fixtures, appliances, and devices are installed, operable, connected, and tested. Skipping a required inspection means the work must be exposed again - a favorite exam scenario.
Test methods
DWV systems are commonly tested with water at a head of about 10 ft (or 10 psi) held for at least 15 minutes, or with air at a lower pressure where the code permits, with all openings plugged and the test visible for inspection. Water supply systems are tested at working pressure or a code-specified higher pressure (often 100 psi) held for a set period, with the test water from a potable source. Gas piping is tested with air or inert gas. New potable mains and repaired lines are chlorinated, flushed, and sampled before being placed in service.
Field execution
Support pipe at the code's hanger spacing; allow for expansion; sleeve pipe through masonry and concrete; firestop penetrations of rated assemblies; bed and backfill buried pipe properly; keep the required fall and clearances; and label valves, backflow assemblies, and gas shutoffs. Protect openings, keep debris out, and confirm grade to the fixture.
Traps in questions
Confusing a rough-in approval with final approval; testing a drain system without plugging the lowest opening; forgetting to test backflow assemblies and record the results; and assuming a repair needs no permit when the code classifies it as an alteration.
Rule of thumb
If the work will be concealed, it must be inspected first. If it carries water, gas, or waste, it must be tested before it is covered or energized - and the test must be documented.