A plumbing top out inspection is the rough-in check after framing and piping are in place, before insulation or drywall conceals the work. Drain and vent piping gets its required test, often a 10-foot water head, while water supply piping gets a separate pressure test. Obtain approval before covering the work.
When does the top out inspection happen?
After framing and before the walls close. Phoenix's residential inspection checklist places the plumbing check at the pre-drywall stage, with the piping exposed. Chandler lists its plumbing rough-in as Rough Plumbing/Topout. Confirm the required inspection stages for your permit before covering the work; commercial approved plans and local procedures may add inspections.
It sits in the middle of the plumbing inspection sequence:
| Stage | What is open | Inspection purpose |
|---|---|---|
| Underground | Trenches, under-slab drain and water lines | Inspect the work before backfill covers it |
| Top out (rough-in) | Pipes in walls, ceilings, and chases, vents through the roof | Inspect exposed piping and required tests before concealment |
| Final | Fixtures set, water on, building done | Inspect the completed installation |
Cities give each stage a name and a code for scheduling. Phoenix's residential checklist folds top out into its Pre-Drywall Inspection (625), done together with framing, mechanical, and electrical. Chandler calls it Rough Plumbing/Topout (733). Our page on Chandler's required plumbing inspections lists every code. The last stage is covered in what a plumbing final inspection is.
Obtain the required inspection approval before concealing the work. Phoenix's checklist states for the pre-drywall stage: "Do not insulate, drywall, or cover until approved."
What does the inspector test at top out?
The drain and vent system goes under a water test or an air test, and the water supply piping goes under a pressure test. Have the required tests ready for the inspector to observe. The contractor or permit holder arranges the test setup and inspection under the local permit process.
Drain and vent water test (IPC 312.2). The plumber plugs every opening except the highest one and fills the system with water "to the point of overflow." The code says sections "shall not be tested with less than a 10-foot (3048 mm) head of water," and "This pressure shall be held for not less than 15 minutes. The system shall then be tight at all points." Phoenix's residential checklist asks for the same thing in shorthand: "Do a top-out 10' water test inspection and a shower liner test." On a multistory building, the plumber tests in sections, and the code requires that the upper 10 feet of each earlier section be retested with the next one, so every joint sees the full head.
Drain and vent air test (IPC 312.3). Air pressure of 5 psi held for 15 minutes is the alternative, but not for plastic pipe. The code says "Plastic piping shall not be tested using air." For PVC or ABS drainage piping, use the permitted water test rather than pressurizing plastic with air.
Water supply test (IPC 312.6). The supply piping "shall be tested and proved tight under a water pressure not less than the working pressure of the system; or, for piping systems other than plastic, by an air test of not less than 50 psi." Again, the test holds for at least 15 minutes. Phoenix's checklist says simply: "Water supply system shall be pressure tested."
Shower liner test (IPC 312.10). Where a shower pan is built with a liner, the drain is plugged and the pan is flooded. The code requires the water to be at least 2 inches deep at the threshold and held for 15 minutes.
What else does the inspector check?
Beyond the tests, the inspector looks at how the pipe was installed. From Phoenix's pre-drywall checklist and the IPC, the usual items are:
- Slope on drain lines. Verify the applicable code, local amendments and approved plans. Phoenix's residential checklist summarizes drainage slope as 1/4 inch minimum; IPC Table 704.1 has different minimum slopes by pipe size, and Phoenix also amends grease-waste piping. The checklist shorthand is not a substitute for those requirements.
- Pipe sizing for the fixture load, and correct fittings for each change of direction.
- Vents sized and routed correctly, with each fixture vented and the stacks through the roof.
- Protection from nails. The checklist wants piping protected from nail damage at studs, rafters, and joists, which means steel plates where pipe runs close to the face of the framing.
- Support and stress. "Piping shall not be subjected to undue stress."
- Corrosion protection where pipe passes through concrete or masonry.
- Shutoffs. Phoenix's list reads: "Fullway valve required at inlet to water heater and to the dwelling unit."
- Cleanouts where the code requires them.
On a commercial job, the inspector also checks the rough-in against the approved plans, since the fixture count and pipe sizes were reviewed at permit. That includes grease waste lines, indirect waste for kitchen equipment, and any backflow assembly locations.
### How do you request a top out inspection in Phoenix?
Phoenix schedules inspections by phone. The residential checklist says to call (602) 495-0800 with the permit number, the address, and the inspection type, and "Requests received before 9:00 p.m. (Monday-Friday) will normally be inspected the following workday." Have the water test filled and holding before the inspector's window opens.
Why do jobs fail a top out inspection?
Items that can require correction include:
- 1The test isn't on. The inspector shows up and the stack isn't filled, or the gauge isn't on the supply lines. With no test to observe, there is nothing to pass.
- 2The test won't hold. The water level drops in the stack, or the gauge falls. That usually points to a missed glue joint, a loose test plug, or a cracked fitting.
- 3Missing nail plates where the pipe runs close to the edge of a stud.
- 4Wrong slope or a belly in a horizontal drain.
- 5Vent problems: a fixture with no vent, a vent tied in too low, or an undersized vent.
- 6Plan mismatch on commercial jobs: fixtures moved or added without a revision.
When the inspector identifies a deficiency, follow the correction notice, make the repair and request the required reinspection. Phoenix's checklist is intended to help customers avoid deficiencies and reinspections. A reinspection holds up every trade waiting to close the walls.
Who is responsible for the top out inspection?
The permit holder coordinates the required inspections with the contractor and local building department. The plumber sets up and runs the tests, schedules the inspection, meets the inspector (or leaves the test holding), and makes any corrections. The general contractor coordinates it with the framing, mechanical, and electrical rough-ins. In Phoenix those are inspected at the same pre-drywall visit, so one trade's miss can hold up everyone.
For an owner-builder or a homeowner doing an addition, the same rules apply to you as the permit holder. Our page on permits for new construction plumbing in Phoenix covers who can pull the permit.
HQ Plumbing & Air handles rough-in plumbing, required testing and inspection preparation for commercial build-outs, tenant improvements, and additions across the Phoenix area. We're licensed and insured, with free estimates and upfront pricing. See our commercial plumbing services.
Pipes in, test holding, inspector signs off. Then the walls can close.