The Complete Plumbing Rough-In Inspection Checklist (IPC & UPC)

The rough-in inspection is one of the most critical checkpoints in any plumbing project. It's your chance to verify that everything behind the walls is code-compliant before drywall goes up and hides it forever. Fail this inspection and you're ripping out work. Pass it, and the rest of the project flows.

This checklist covers the essential items an inspector is looking at during a plumbing rough-in, organized by system. It references both the International Plumbing Code (IPC) and the Uniform Plumbing Code (UPC), since roughly half the country follows each one.

Before the Inspector Arrives

Permit and Plans

• ☐ Active plumbing permit posted on site — No permit, no inspection. Full stop.
• ☐ Approved plans on site — The inspector will compare your installation to the approved drawings. If you made field changes, you may need a plan revision.
• ☐ Inspection request submitted — Most jurisdictions require 24-48 hours notice. Some have online portals, others require a phone call.

General Conditions

• ☐ All rough-in work is complete — Don't call for an inspection with half the system stubbed out. Every drain, vent, and water line shown on the plans should be installed.
• ☐ System is accessible for inspection — No insulation covering pipes, no drywall partially installed. The inspector needs to see every joint, hanger, and connection.
• ☐ System is under test — The DWV system must hold a test pressure for the duration of the inspection. Have the test set up BEFORE the inspector arrives.

DWV (Drain, Waste, and Vent) System

Testing

• ☐ Air test or water test in place — IPC Section 312.2 and UPC Section 712.1 require testing of the DWV system.
• Water test: Fill the system with water to the highest point (at least 10 feet of head or 5 PSI). All joints must hold for a minimum of 15 minutes with no visible leaks.
• Air test: Pressurize to 5 PSI gauge. The system must hold pressure for 15 minutes. (Note: some jurisdictions don't allow air tests on DWV.)
• ☐ Test gauge visible and holding — The inspector will verify pressure hasn't dropped. Have the gauge where they can see it without a ladder if possible.

Pipe Sizing and Slope

• ☐ Drain pipe sizes match plans and code — IPC Table 710.1(2) / UPC Table 703.2. Common minimums:
• Lavatory: 1-1/4" (IPC) or 1-1/2" (UPC)
• Shower: 2"
• Toilet: 3" (can be 4" for building drain)
• Kitchen sink: 1-1/2" minimum, 2" recommended
• ☐ Proper slope on horizontal drains — IPC Section 704.1 / UPC Section 708.0:
• Pipe 3" and smaller: 1/4 inch per foot minimum
• Pipe 4" and larger: 1/8 inch per foot minimum
• ☐ No sags or bellies in horizontal runs — Consistent slope throughout. A belly collects water and debris, leading to stoppages.

Venting

• ☐ Every fixture is vented — IPC Section 904 / UPC Section 901. No exceptions. Every trap needs a vent to prevent siphoning.
• ☐ Vent sizes meet minimum requirements — IPC Table 916.1 / UPC Table 703.2. The minimum vent size is generally 1-1/4" (IPC) or 1-1/2" (UPC), but it depends on the fixture unit load.
• ☐ Trap arm distances within limits — The distance from the trap weir to the vent must not exceed the code maximum:

• ☐ Vent termination height noted — Vents must extend through the roof to the outside. Minimum 6 inches above the roof surface (IPC 903.1), or higher in snow regions per local amendments.
• ☐ Vent grade slopes back to drain — Dry vents installed horizontally must slope back toward the drain they serve at a minimum of 1/4 inch per foot to prevent moisture accumulation.

Fittings and Connections

• ☐ Correct fittings used on drainage — Drainage fittings only (long-turn, sanitary tees, wye fittings). No vent tees or short-turn elbows on horizontal drains.
• ☐ No sanitary tees on their back — A sanitary tee installed horizontally (on its back) is a code violation. Use a wye with a 45-degree bend instead.
• ☐ Proper cleanout locations — IPC Section 708 / UPC Section 707. Required at the base of each stack, at each change of direction greater than 45 degrees, and every 100 feet on horizontal runs (IPC) or per local requirements.
• ☐ All joints properly made — Solvent cement joints fully seated, no dry-fitted connections. Mechanical joints properly tightened. No-hub couplings with proper torque.

Support and Hangers

• ☐ Pipe adequately supported — IPC Table 308.5 / UPC Table 313.3:
• ABS/PVC horizontal: every 4 feet
• Cast iron horizontal: every 5 feet (10 feet for hubless)
• Copper DWV horizontal: every 6 feet
• ☐ Vertical pipe supported at each floor level
• ☐ Hangers are appropriate material — No wire hangers, no zip ties. Metal hangers or approved pipe clamps. Dissimilar metal isolation where required (e.g., copper pipe with non-copper hangers needs insulation).

Water Supply System

Testing

• ☐ Pressure test in place — IPC Section 312.5 / UPC Section 609.4. The water supply system must hold test pressure for the required duration.
• Typical: 80 PSI (or working pressure plus 50%, whichever is greater) for a minimum of 15 minutes with no drop.
• ☐ Test gauge visible and holding

Pipe Sizing and Layout

• ☐ Main supply line sized correctly — Typically 3/4" or 1" for residential, based on fixture count and distance.
• ☐ Branch lines sized correctly — 1/2" minimum for most individual fixtures, 3/4" for bathtubs and showers per IPC Table 604.5.
• ☐ Hot and cold lines properly oriented — Hot on left, cold on right (facing the fixture). This is a code requirement, not a suggestion (IPC 607.4).
• ☐ Proper valve locations — Shutoff valves at each fixture, at the water heater, and at the main. Accessible without removing finished surfaces.

Installation Quality

• ☐ Adequate clearance from drain lines — Water supply lines should be installed above drain lines when running parallel, or at least 12 inches away horizontally. When crossing, the water line must be above the drain line or protected.
• ☐ Pipe supported per code — Copper horizontal: every 6 feet. CPVC horizontal: every 3 feet. PEX horizontal: every 32 inches.
• ☐ Expansion/contraction accounted for — Long runs of CPVC and PEX need room to expand. No rigid clamping that prevents movement.
• ☐ Anti-scald protection planned — Shower valves must be pressure-balanced or thermostatic mixing type per IPC 424.3. Verify the valve is approved.

Gas Piping (If Applicable)

• ☐ Gas pipe sized per IFGC Table 402.4 based on BTU load and pipe length
• ☐ Pressure test in place — Typically 3 PSI for 10 minutes for residential gas piping
• ☐ Sediment traps (drip legs) at each appliance — Tee with capped nipple, minimum 3 inches, at the appliance inlet
• ☐ Shutoff valves at each appliance — Accessible and within 6 feet of the appliance
• ☐ Pipe properly supported — Black iron: every 6-8 feet horizontal, each floor level vertical. CSST per manufacturer requirements.

Common Reasons for Failing a Plumbing Rough-In

Based on conversations with inspectors and field experience, here are the top reasons rough-in inspections fail:

1. Trap arm too long — Especially under the UPC, where distances are shorter than most plumbers expect.
2. Missing or undersized vents — Every fixture needs a vent. Period.
3. Wrong fittings on drainage — Vent tees used on drains, short-turn elbows on horizontal runs.
4. Test not holding — A slow leak you didn't notice will show up on the gauge. Check every joint.
5. Insufficient slope — Eyeballing slope is not acceptable. Use a level or laser.
6. Missing cleanouts — Especially at the base of stacks and direction changes.
7. Hot/cold reversed — Simple mistake, easy to fix, but it will fail you.
8. No permit or wrong plans on site — Administrative, but it stops the inspection cold.

Tips for a Clean Pass

• Walk the system yourself before calling for inspection. Check every joint, every hanger, every slope. Be your own inspector first.
• Take photos of everything before the inspector arrives. If there's a dispute later, you have documentation.
• Have the code book on site or use a digital tool like Trade Code Wizard to reference specific sections during the inspection.
• Be present for the inspection. If the inspector has questions, you can answer immediately rather than scheduling a re-inspection.
• Know which code your jurisdiction uses. IPC and UPC requirements differ significantly in several areas — especially trap arm lengths and minimum vent sizes. Trade Code Wizard covers both codes and lets you toggle between them.

Final Thought

A plumbing rough-in inspection doesn't have to be stressful. If you install per code, test the system, and verify your own work before the inspector arrives, you'll pass the first time. Use this checklist as your pre-inspection walkthrough, and you'll catch the issues before the inspector does.

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This checklist references the 2021 IPC and 2021 UPC. Code editions adopted vary by jurisdiction. Always confirm which code version and local amendments apply in your area.