Homeowner has sewer smell under sink, pays plumber, and commenters ask: 'What plumber?'

Home repair issues can quickly turn into something more serious when a foul sewer smell lingers in a kitchen cabinet, even after a plumber's visit.

That's why one homeowner's unresolved plumbing problem sparked such a strong reaction online. The odor alone was bad enough, but many readers were especially frustrated that a professional had already been called and still left without solving it.

Here's what to know

In a post on Reddit in r/Plumbing, the original poster said, "I've been dealing with a persistent sewer/drain smell coming from the cabinet under my kitchen sink and I can't figure out where it's coming from."

Before asking the forum, the homeowner said the wall opening around the drain pipe had been sealed with expanding foam and that a plumber had already "cleaned the trap/siphon and the accessible drain parts."

One suspected problem area was a large gray corrugated pipe that dropped into a pronounced U-shaped loop, which the poster wondered could be collecting stagnant water or buildup. They said the odor seemed strongest inside the cabinet rather than at the sink drain.

"What plumber looks at this, agrees to clean the trap and then just walks away?" one commenter wrote.

More background

While online commenters can't confirm the exact cause from photos alone, one pointed to corrugated drain tubing as a likely source.

"Corrugated pipe is fantastic at holding old food, grease, odor creating bacteria and what not. So switching out both the Grey(gray) and white pipe for smooth walled pipe, the white pipe can probably be a flexible tubing such as a rubber hose used for dishwashers, and the Grey pipe, including the strange grey(gray) drain pipe coming directly from the sink basin, switch those out for a rigid smooth walled pipe set up and a better 'basket strainer' to hook everything up to the bottom of the sink basin," one commenter said.

What can be done?

A second opinion from a plumber willing to assess the full drain configuration, not just clean one accessible section, may be necessary.

The bigger issues appeared to be whether the trap was set up correctly and whether the corrugated pieces should be replaced with smooth-walled pipe.

Several comments suggested the system could be improperly configured even if it still drains.

"That grey vacuum cleaner hose or whatever is probably full of water. I would guess that trap can be oriented differently and the gray tube made shorter and more direct," as one commenter put it.

Where can I learn more?

For more on the kinds of sink and drain issues that can lead to bad smells or bigger plumbing headaches, these stories are a good place to start. They cover under-sink pipe cleaning, simple drain maintenance, and stubborn sink clogs homeowners tried to fix.

• A homecare expert shared advice on preventing clogs and foul sink odors.

• One homeowner swore a simple hot-water trick helped keep drains clear.

• A homeowner learned too late when a major mistake clogged the kitchen sink.

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