Remodels change drains and vents. Common causes are capped or abandoned lines left open, a moved fixture whose trap or vent was altered, a new floor drain with no primer, or debris in a vent. It also can be a fixture that was disconnected and never sealed. A plumber can pressure test and trace it.
Common causes after a build-out
- 1An open or poorly capped line. A demolished sink, floor drain or mop sink can leave a pipe stub that was never sealed. Gas escapes into the wall or ceiling and drifts into the suite.
- 2A moved fixture. New restroom or sink locations need new trap arms and vents. If a vent was left off or connected wrongly, traps can siphon dry.
- 3A new floor drain with no primer. A floor drain that never gets water evaporates dry quickly. The 2024 International Plumbing Code, as adopted in Phoenix, Section 1002.4.1, requires protection for seals subject to evaporation.
- 4A cracked pipe under the slab. Saw cutting and trenching for new drains can damage nearby lines.
- 5Construction debris in a vent or a loose cleanout cap.
- 6Ventilation changes. A new exhaust fan can pull gas through an opening that the old airflow never touched.
Was the system tested?
Chapter 7 of the code says the sanitary drainage system must be tested under Section 312 before use, and the permit inspection is the point where that is checked. If the alteration was done without a permit, or the inspection was skipped, that test may never have happened. See commercial tenant improvement plumbing for how the process works.
Finding the opening with a smoke test
After a build-out, a smoke test can help find an open stub, an unsealed capped line or a missing vent connection. HQ uses professional liquid-smoke equipment that forces air into the vent system and fills the piping with smoke, so the crew can look for unexpected escape points.
What to do
- Fill all traps, including any new ones, and recheck the next day.
- Ask your contractor for the permit and inspection records.
- Have a plumber test the drain and vent system and inspect any capped stubs.
- If the smell is strong, leave the affected area first and arrange assessment before reentry.
Who pays
That depends on who did the work and what your lease says. Our landlord or tenant page covers how to read it. Keep dates and photos.
A safety note
Hydrogen sulfide is what you smell, and ATSDR points out that people can lose the ability to smell it at higher levels. A smell that disappears is not proof it is gone. HQ offers 24/7 service, is licensed and insured, and gives free estimates and upfront pricing.
A smoke result identifies an air path under the test conditions. Obstructions, soil and concealment can limit visibility, so no visible smoke does not rule out every defect. The crew confirms the cause before assigning a repair or responsibility. See HQ’s plumbing smoke testing.