Sewer smell in a strip mall: how do you find which tenant?

Ask every tenant, including the ones who have not complained. Mark smelling suites on a plan. A cluster along one stretch of the building hints at a specific section of the line. One lone suite points to its own drains.

Each suite should fill its own floor drains, sinks and mop sinks. The 2024 International Plumbing Code, as adopted in Phoenix, Section 1002.4, requires a 2 to 4 inch water seal in each trap, and dry seals are the most common cause, especially in vacant units and storage rooms. Run water and recheck after a day. A vacant suite next door can be the source, so include it. See vacant suite sewer smell.

If traps are full and several suites smell, the shared drain line is the next suspect. The code allows multiple buildings on one lot to share a common building sewer, and a multi-tenant building will often have shared branches. Signs of trouble: slow drains in several suites, gurgling, water standing in a cleanout or backups in the lowest suites. A cleanout is the access point a plumber uses to check for water levels, and to run a camera. See what a sewer cleanout is.

A blocked or damaged roof vent can draw water out of traps as fixtures drain and push gas back in. A roof walk finds this quickly.

When several suites smell and the traps are full, a smoke test can show which suite's piping is leaking. HQ uses professional liquid-smoke equipment that forces air into the vent system, so smoke travels the drain and vent piping in each suite. Smoke showing up inside a particular suite points to a leak in that tenant's piping or seals. Tenants should get notice first so nobody mistakes it for a fire.

A plumber can camera the shared line from a cleanout and mark where a break, offset or blockage sits. That tells you which section, and often which side of the property line or which tenant's branch it is on.

Who pays depends on the lease and on whether the fault is inside a suite or in shared piping. See who is responsible in a commercial lease.

Hydrogen sulfide is what you smell. ATSDR notes it can be noticed at very low levels and that smell can fade as people adapt. A strong smell or symptoms means leave the affected area first and arrange appropriate help. HQ offers 24/7 service, is licensed and insured, and provides free estimates with 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.

For a related odor investigation, see sewer smell in an office restroom: how do you trace it.

For a related odor investigation, see why does only one apartment unit smell like sewer.