An IPC plumbing inspection is a review of a building’s plumbing work against the International Plumbing Code, carried out by a local code official or an authorized third-party inspector. The International Plumbing Code is a model code published by the International Code Council that most U.S. jurisdictions adopt whole or with local amendments. The inspector walks the site, compares what’s installed against the approved plans, and confirms that pipes, fittings, fixtures, and tests meet the code’s minimum standards. Plumbing work almost never gets a single inspection. It gets several, staged to the construction, and each one has to pass before the next part of the job can proceed.
The Three Inspection Phases
Most jurisdictions require at least two separate inspections during construction, and larger projects require three or more. The phases exist because the inspector has to see things while they are still visible. Once concrete is poured or drywall is hung, verification gets expensive.
Underground or Slab Inspection
Before concrete is poured for a slab foundation, all drainage and supply piping running below or within the slab must be in place and fully exposed. The inspector checks pipe routing, material, slope, and connections. Only after this phase passes does the vapor barrier go down and the concrete get poured. Pipes buried outside the building must sit at least 12 inches below grade and no less than six inches below the local frost line, whichever is deeper.1International Code Council. 2024 International Plumbing Code – Chapter 3 General Regulations In northern climates, that can push required depth to three feet or more. Work buried without inspection can be ordered re-excavated.
Rough-In Inspection
The rough-in inspection happens after supply, drain, and vent piping is installed inside walls, floors, and ceilings, but before insulation, drywall, or finish material covers anything. Every joint, connection, hanger, and fitting must be visible. The inspector compares the physical installation to the approved plans and verifies that required pressure tests are in place and holding. No walls close up until this phase passes.
Final Inspection
After fixtures, faucets, water heaters, and appliances are installed and connected, the final inspection confirms the system works as a whole. The inspector runs water at every fixture, looks for leaks, checks hot water temperature limits, and verifies water heater safety devices. This is the last gate before occupancy.
Pressure Tests You Have to Run
The IPC puts the testing on the permit holder, not the inspector. You supply the equipment, gauges, and labor, and you keep the system under pressure until the inspector arrives to witness the result.2International Code Council. 2024 International Plumbing Code – 312.2 Drainage and Vent Water Test
The drainage and vent water test fills the system with water to a minimum of 10 feet of head pressure, measured from the highest point being tested. All openings are plugged except the highest, where water enters. The system must hold with no leaks at any joint for at least 15 minutes.2International Code Council. 2024 International Plumbing Code – 312.2 Drainage and Vent Water Test When testing in sections, the upper 10 feet of the previous section is retested as each new section goes in, so virtually every joint sees the full test pressure.
An air test at 5 psi for at least 15 minutes is an alternative on the drain and vent side, with one important restriction: plastic piping cannot be air tested. The pressure buildup in PVC and ABS creates a safety risk if a joint fails, so those systems have to be water tested.3International Code Council. 2024 International Plumbing Code – Chapter 3 General Regulations – Section 312.3 Any adjustments for temperature or gasket seating have to happen before the 15-minute clock starts.
Once the potable water piping is complete, it gets its own test: water pressure at least equal to the system’s working pressure, or air at 50 psi for non-plastic piping, held for at least 15 minutes. Test water must come from a potable source.4International Code Council. International Plumbing Code – 312.5 Water Supply System Test
What the Inspector Actually Checks
The IPC organizes plumbing into separate systems, each with its own chapter, and the inspector works through them item by item against the approved plans.
Water Supply and Distribution
Chapter 6 covers everything from the water service at the building to the last fixture connection. The inspector verifies that pipe materials are approved for potable water, that pipe sizes match the demand for fixtures served, and that backflow prevention is installed wherever the potable supply could contact a contamination source. The code requires an air gap of at least one inch, or twice the pipe diameter if that is greater, between a water outlet and the flood-level rim of a fixture to prevent back-siphonage.5International Code Council. 2024 International Plumbing Code – Chapter 9 Backflow Protection Outdoor spigots need vacuum breakers. Carbonated beverage dispensers in commercial settings need their own dedicated backflow devices.
Sanitary Drainage
Chapter 7 governs the waste piping. The inspector checks that horizontal drains slope enough to move waste by gravity without pooling, that diameters match fixture load calculations, and that cleanouts sit at required intervals. Horizontal drains need a cleanout at least every 100 feet, and any change of direction greater than 45 degrees also requires one.6UpCodes. GSA Plumbing Code 2024 – Chapter 7 Sanitary Drainage The junction between the building drain and the building sewer gets its own cleanout.
Vents and Traps
Chapter 9 addresses the vent piping that lets air into the drainage system to equalize pressure. Without it, water seals in fixture traps get siphoned and sewer gases enter living spaces. Vent pipes have to extend at least six inches above the roof and sit far enough from operable windows. Every fixture trap has to maintain a water seal between two and four inches deep.7International Code Council. 2018 International Plumbing Code – Chapter 10 Traps, Interceptors and Separators
Hangers and Support
Pipe hangers have to be spaced at specific intervals depending on material. PVC needs horizontal support every four feet. Copper can span up to 12 feet between hangers.8International Code Council. International Plumbing Code – 308.5 Interval of Support Missing or incorrectly spaced hangers are a common rough-in failure.
Plan Deviations
Unauthorized deviations from the approved drawings are a common reason for failure even when the actual work is technically sound. If something changed in the field, the plans need to change with it before the inspection, not after.
What Gets Added at the Final Inspection
The final inspection is more detailed than many contractors expect. By this point every fixture, appliance, and water heater is installed and operational. The inspector runs water through every fixture, checks for leaks at connections, verifies that hot water controls are on the left side of each fixture, and confirms that fixtures are sealed to walls and floors.
Water Heaters
Water heaters draw heavy scrutiny. The temperature and pressure relief valve must be installed, and its discharge pipe has specific rules: it can’t be trapped, can’t connect directly to the drainage system, must discharge through an air gap, and must terminate where someone can see it. The discharge pipe cannot be smaller than the valve outlet and must flow by gravity to the floor, a drain pan, a waste receptor, or outdoors.9International Code Council. International Plumbing Code – 504.6 Requirements for Discharge Piping Tank-type heaters also need a drain valve at the bottom with a minimum three-quarter-inch inlet and a garden hose thread on the outlet.10International Code Council. 2024 International Plumbing Code – Chapter 5 Water Heaters
Thermal Expansion Control
If the water supply has a check valve, pressure-reducing valve, or backflow preventer upstream of the water heater, the system is considered closed and thermal expansion has nowhere to go. The IPC requires a thermal expansion control device on the cold water supply feeding the heater, installed downstream of all check valves and backflow preventers.11International Code Council. 2021 International Plumbing Code – 607.3 Thermal Expansion Control The tank must be sized per the manufacturer’s instructions, and the resulting pressure can’t exceed the code’s maximum for the distribution system. This is one of the most commonly missed items on final inspections.
Temperatures and Clearances
Shower and bathtub water temperature generally can’t exceed 120°F. Combination water heating systems that run space heating above 140°F need a mixing valve to keep the potable hot water distribution at 140°F or less.10International Code Council. 2024 International Plumbing Code – Chapter 5 Water Heaters Toilets typically need 15 inches from center to the nearest wall and 21 inches of clear space in front, and shower doors must provide at least a 22-inch clear opening.
Scheduling and the Day of the Inspection
You schedule the inspection once the work is ready for the phase. Most jurisdictions require at least 24 hours’ notice through an online portal or phone system. On the day, the inspector arrives, walks the site, reads the gauges to confirm the test pressure held with no drop, examines visible joints, verifies materials and sizes, checks hanger spacing, and confirms that required components like cleanouts and backflow preventers are in place.
If everything checks out, the phase is approved and you can close walls, pour concrete, or move to the next stage. If it fails, you receive a written notice listing the specific violations and the steps to schedule a re-inspection. The project can’t advance until the corrections pass.
Commercial Projects Have More to Check
Commercial work triggers inspection items that residential work does not. Any commercial food preparation area, including restaurants, hotel kitchens, school cafeterias, and hospital kitchens, must have a grease interceptor or automatic grease removal device on fixtures that discharge fats, oils, or grease.12International Code Council. International Plumbing Code – Chapter 10 Traps, Interceptors and Separators Healthcare facilities with medical gas piping fall under a separate certification regime under the ASSE 6000 series standards and are not handled by a general plumbing inspector. If your project involves either, expect additional inspection scope beyond the standard IPC walk-through.
If You Fail, and If You Disagree
Inspection failures are common and usually not catastrophic. Most involve a missing hanger, a joint that didn’t hold pressure, an unapproved material substitution, or a plan deviation. You fix the item, call for a re-inspection, and move on. A failed inspection that requires a return visit often triggers an additional fee.
Working without a permit is a different matter. The IPC requires anyone who installs, enlarges, alters, or replaces any part of a plumbing system to pull a permit from the local code official before the work starts.13UpCodes. GSA Plumbing Code 2024 – Chapter 1 Scope and Administration Stopping a leak in an existing drain or water pipe, clearing a clog, or replacing a faucet is exempt as long as you aren’t rearranging or replacing piping. When a code official finds unpermitted work, the official can issue a stop-work order that halts construction until violations are resolved, and you can be required to open finished walls or re-excavate buried lines so the hidden work can be verified.
If you believe the inspector misinterpreted the IPC, that the code doesn’t fully apply to your situation, or that your method is equally good or better, you can appeal to the board of appeals.14International Code Council. 2021 International Plumbing Code – Appendix F Board of Appeals The appeal must be filed within 20 days after you’re served with the notice of violation. Filing generally pauses enforcement of the order, with one exception: if the violation involves an imminent danger, the order stays in effect while the appeal is heard. The board can hear evidence from both sides, but it has no authority to waive code requirements outright.15International Code Council. 2021 International Building Code – Appendix B Board of Appeals An appeal is a tool for a genuine dispute over how the code was applied, not a route around compliance.