The smell hit as soon as she walked into her apartment. It came from the kitchen sink and the cabinet underneath, disappeared at times, then returned. She described it as “putrid gas” and said she smelled it every day.
Reddit user u/PieRadiant8724 posted photos of the plumbing under her sink to r/CleaningTips. Instead of recommending another cleaner, commenters started pointing at one section of pipe visible in the pictures: an opening that appeared to have nothing on top of it.
Reddit noticed the open pipe
One of the top responses asked whether a vent was missing from the Y-shaped section of plumbing. Another commenter went straight to the concern: the pipe appeared open.
A different commenter explained what they were seeing. The PVC fitting appeared to be missing something at its upper opening, which could allow sewer gas to escape beneath the sink. They recommended having a plumber inspect the setup rather than assuming buildup was the only cause.
That changed the problem from something inside the sink bowl to something beneath it.
The P-trap couldn’t block an opening after it
The curved pipe under a sink has a job beyond carrying water away.
Water stays inside the P-trap and creates a barrier between the room and gases farther down the drain. One commenter pointed out that an open fitting elsewhere in the drainage setup could bypass that barrier.
In other words, cleaning the sink wouldn’t address an opening that allowed odors into the cabinet from another point in the plumbing.
Commenters kept mentioning an AAV
As the discussion continued, one term appeared again and again: air admittance valve, or AAV.
One commenter suggested that the fitting should have an AAV rather than remain open. Another said an old valve may have been knocked off or removed.
Later in the thread, a commenter who identified themselves as a professional plumber gave the same assessment. They said the open drain line was allowing sewer gas into the cabinet and that an air admittance valve belonged on the opening.
Several other commenters independently identified a missing AAV or Studor vent in the same area.
She had already asked maintenance for help
This wasn’t a smell she had ignored.
The renter said she had complained three times and submitted maintenance requests, but the odor remained.
Other possibilities came up in the discussion, from a dirty garbage disposal and dishwasher hose to rotting food or even a dead rodent. One commenter noticed buildup in the dishwasher drain hose, while others suggested cleaning the disposal.
But the open plumbing fitting kept drawing attention because it was visible in the photos.
This wasn’t a job for another bottle of cleaner
The thread doesn’t include a final update confirming that installing an AAV stopped the smell, so we can’t say Reddit proved the cause.
What the photos did reveal was a plumbing detail worth having checked.
When an odor seems to come from a kitchen drain, the instinct is to pour something into it. This renter’s photos sent the discussion in another direction: open the cabinet and inspect what’s happening after the water leaves the sink.
If an open drain fitting, missing vent, or other plumbing problem is involved, another round of baking soda, drain cleaner, or deodorizer won’t put the missing plumbing part back.
For a renter, that means documenting the problem and getting maintenance or a plumber involved rather than modifying drain plumbing without knowing how the system was meant to be vented.
Would you have noticed the open pipe under this sink, or assumed the drain needed another cleaning?
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