UPC Section 712 requires new drain, waste, and vent piping to pass a leak test before the walls are closed. The plumber uses a water test with at least a 10-foot head of water, or an air test at 5 psi. The pipe must hold the test for 15 minutes with no leaks while the inspector watches.
The Uniform Plumbing Code is published and copyrighted by IAPMO. This page explains the section in our own words with a short excerpt only. Read the full official text at the source.
New drain pipe gets buried in walls, floors, and slabs. Once it is covered, a leak is hard and costly to find. So the code checks the pipe before it disappears. UPC Section 712 sets how a plumber proves that new drain, waste, and vent (DWV) piping is watertight. The pipe has to pass a leak test while an inspector watches. Only then can the walls close.
What this section covers
Section 712 is titled Testing Procedures for Drain, Waste, and Vent Piping:
712.0 Testing Procedures for Drain, Waste, and Vent Piping
The test happens after the rough piping is in but before it is covered. The plumber seals off the system and puts pressure on it. If the pipe holds pressure with no drop, it has no leaks. If the pressure falls, there is a leak to find and fix. The code allows a water test or an air test, and it sets rules for both.
The water test
For the water test, the plumber plugs the bottom of the system and fills the pipes with water. Every part of the system must hold at least a 10-foot head of water. A "head" is just the height of the water column above the point being tested. That height creates the pressure. The water sits in the pipe for at least 15 minutes. The inspector then checks that the water level has not dropped and that no joint drips.
The air test
An air test is the common choice for plastic DWV pipe and tight spaces. The plumber caps the openings and pumps in air to a gauge pressure of 5 psi, which is about the same push as a 10-inch column of mercury. That pressure has to hold for 15 minutes with no extra air added. A gauge that holds steady means the pipe is tight. Note that plastic pipe is not tested with air in every case, and some plumbers use a vacuum test on plastic instead.
The building sewer
The line that carries waste from the house to the city main gets its own check. Section 723 covers the Building Sewer Test. That test makes sure the buried sewer lateral is sealed and holds water before it is backfilled.
What this means for you
If you are building, remodeling, or moving drains, plan for this inspection. The pipe cannot be covered until it passes. A failed test means finding the leak and testing again, which adds time. This is also why a licensed plumber pressure-tests work rather than eyeballing it. For the permit steps, see new construction plumbing permits in Phoenix. Testing pairs with correct grade and fittings, so see drain pipe slope and changes of direction. To learn how leaks are traced later, see how plumbers find hidden leaks.
Full text and source
UPC Section 712 is part of the Uniform Plumbing Code. IAPMO publishes it and holds the copyright, so only the section headings and short notes are shown here. The test values above are described in plain terms, not quoted. Phoenix enforces the 2024 UPC with local amendments. Read the section on the UPC viewer at UpCodes, review the official code at IAPMO, or confirm local amendments with the City of Phoenix Planning & Development Department at phoenix.gov/pdd.
Keep Reading
- UPC 1003: Which Fixture Traps Are Allowed (and Banned)
- UPC Section 1101: Storm Drainage and Roof Runoff
- UPC Section 603: Cross-Connection Control and Backflow Protection
- UPC 705: Joints and Connections in Drainage Piping
- What plumbing permits and inspections does new construction need in Phoenix?
- How do plumbers find a hidden or slab leak?
- Why does my bathroom drain smell like sewer?