What is the difference between IPC and UPC?

IPC is published by ICC (part of the I-Codes family); UPC is published by IAPMO. Both cover the same scope but diverge on specific values — DFU tables, vent rules, AAV acceptance, etc.

Which states use IPC vs UPC?

Adoption is roughly geographic — the West Coast and parts of the Mountain West lean UPC, while the rest of the country tends toward IPC. See the state landing pages for exact adoption.

Are air-admittance valves (AAVs) allowed in both codes?

AAVs are explicitly permitted by the IPC under §917. The UPC historically prohibits them in most applications, with some jurisdiction-by-jurisdiction exceptions.

IPC / UPC Practice Questions — International & Uniform Plumbing Code

Free practice questions on the International Plumbing Code (IPC, published by ICC) and the Uniform Plumbing Code (UPC, published by IAPMO). Every question is tagged with the code family it applies to, plus a section reference in the answer key. Roughly half the U.S. adopts one or the other (with state amendments); a few states publish their own derived code (CPC in California, OPSC in Oregon). Use this set to drill code-family-specific differences — air-admittance valves are an IPC concept, for instance, while the UPC has unique vent-sizing tables.