Confirm whether the jurisdiction enforces the UPC or another plumbing code, and which edition. Then trace fixtures, water supply, drainage and vent routes, water heaters, and special wastes through the plumbing plans, isometrics, schedules, and the architectural and structural drawings. AI can flag conflicts; the plumbing engineer and code official decide compliance.
What does the UPC cover?
IAPMO describes the Uniform Plumbing Code as developed to govern the installation and inspection of plumbing systems, and its companion, the Uniform Mechanical Code, as providing the same governance for mechanical systems.
IAPMO announced on June 11, 2026 that it has published the 2027 editions of the UPC and UMC, and its online reading page links online versions of its codes. The California Building Standards Commission states that the UPC and UMC become the California Plumbing Code (Title 24, Part 5) and California Mechanical Code (Part 4). Checked October 5, 2026. Record the edition the jurisdiction enforces, not the newest.
Jurisdictions that adopt the IPC follow the IPC guide; the two codes differ, so one set should not mix them. California projects also follow the California Building Code guide, and fixture counts are explained in how plumbing fixture count requirements work.
Gather the plumbing set and the sheets it crosses
Collect the plumbing plans and the water, waste, and vent isometrics or risers, the fixture schedule, water heater and equipment schedules, the plumbing general notes naming the code, the architectural plans and enlarged toilet rooms, structural plans for penetrations and slab openings, the civil utility plans for the building connections, and the plumbing specification sections.
The plumbing notes, mechanical notes, and code analysis can each name a plumbing code. Check that they name the same one.
Trace the plumbing through the set
| Review question | Sources to compare | Decision to record |
|---|---|---|
| Plumbing code and edition | Code analysis, plumbing notes, mechanical notes, specifications | Confirm every discipline cites the same plumbing code and edition. |
| Fixtures | Fixture schedule, architectural plans, enlarged toilet rooms | Match fixture types and counts between the schedule and the plans. |
| Water supply | Plumbing plans, isometrics, equipment schedules, civil utility plans | Trace the supply from the building connection to the fixtures and equipment. |
| Drainage and venting | Plumbing plans, waste and vent isometrics, sections | Follow each drain to its destination and check that vents are drawn. |
| Openings and slopes | Structural and foundation plans, plumbing plans | Find sumps, trenches, and penetrations shown in only one discipline. |
| Water heating and special wastes | Equipment schedules, interceptor details, specifications | Confirm interceptors and water heaters match across schedules, plans, and details. |
The plumbing drawing checklist is the working log, and fixtures follow the plumbing fixture specifications guide. Groundbook’s published residential plumbing review shows drainage destinations that conflicted between sheets Mechanical work in the same jurisdiction is often under IAPMO’s mechanical code; see the UMC guide.
Example: two plumbing codes in one set
Published finding. In Groundbook’s published neighborhood grocery review, the plumbing cover sheet specified the International Plumbing Code while the mechanical notes called for the Uniform Plumbing Code. The same finding noted building and concrete code editions that differed between disciplines.
Building, concrete, and plumbing code editions do not match. Confirm the code basis on the permit and make each discipline’s notes use that basis.
The design team confirms which plumbing code the jurisdiction enforces and corrects the notes. Fixture, drainage, and venting questions are then checked against one code instead of two.
Review plumbing drawings with Groundbook
Upload the current drawings and specifications to Groundbook, and state the edition, amendments, and review scope in your instructions. Add the UPC edition the project uses from a copy you are licensed to use, where the license permits uploading it, and the jurisdiction’s published amendments. See how Groundbook works with local and licensed codes.
Compare the plumbing code and edition named in the code analysis, plumbing notes, mechanical notes, and specifications, then compare the fixture schedule, plumbing plans, isometrics, equipment schedules, and the architectural, structural, and civil drawings. Flag mixed plumbing codes, fixtures that differ between schedule and plans, drains without destinations, and openings shown in only one discipline. Use the supplied UPC edition and local amendments and cite both sources.
Groundbook links each potential finding to the sheets involved. Verify the plumbing code the jurisdiction enforces before sending a comment.
Document review does not size piping, calculate fixture units, or replace the plumbing engineer or the code official.