How a drain keeps sewer air out
Every sink, tub, shower, floor drain and washer standpipe has a curved trap that holds water. That small pocket of water is the only thing stopping sewer air in the drain line from entering the room. When nobody uses a fixture for weeks, the water evaporates. Aurora's low humidity and warm vacant houses in summer, or furnace-dried air in winter, speed that up.
The drains most likely to dry out are the ones nobody remembers: a basement floor drain, a guest bath shower, a utility sink, a laundry standpipe behind a moved washer. One dry trap is enough to make a house smell like sewer, especially if the HVAC return is nearby.
If refilling every trap does not clear the smell within a day, the problem may be a cracked or disconnected vent pipe, a failed wax ring under a toilet, a cleanout missing its cap or a blocked plumbing vent on the roof. Those call for a plumber.
Drains to check in a vacant rental
| Fixture | Why it dries or fails | What to do |
|---|---|---|
| Basement floor drain | Rarely gets water; often forgotten | Pour water in; ask a plumber about a trap primer or seal if it dries repeatedly |
| Unused shower or tub | Guest baths sit idle even during tenancy | Run water for a minute; check the tub overflow gasket |
| Washer standpipe | Exposed once the tenant's washer leaves | Fill the trap; cap or cover the opening if left empty |
| Toilet base | Wax ring fails, especially if the toilet rocks | Check for movement and staining; plumber if loose |
| Kitchen sink and disposal | Food residue in the disposal and trap | Run water, clean the disposal splash guard |
| Cleanout plugs | Missing or loose caps open the line | Look in the basement or crawl space; replace caps |
| AC condensate drain | Trap dries during cool months | Ask the HVAC technician to check it |
Keeping traps sealed through the vacancy
Fill every drain on day one
Walk the house and run water into every fixture and floor drain, including the ones that seem unimportant.
Add them to the vacancy check
Whoever checks the property during the vacancy should run water at each drain every week or so, more often in hot weather.
Ask about longer-lasting options
For a long vacancy, a plumber can suggest products that slow evaporation or a permanent fix for a chronically dry floor drain.
Retest before the showing
Run every fixture the day before photos or a showing, then do a closed-up smell test.
General information for Aurora, not a quote or professional advice. In an emergency, call 911.