Foul Odor Two

We had a similar question some time ago but I can't remember the detail.

You may however investigate the following.

Porcelain basins have cavities inside and any moisture will be trapped there and may Emmit a terrible odor.

I have suspected that there may be something of this nature occuring, but I am unsure how to proceed short of replacing the fixture. As I did not have this problem prior to the installation of this basisn (by a professional), it makes some sense.

Yeah the vent tube is likely. Also the water itself could be fouled.

Ironically my ex-wife called yesterday. Seems her downstairs is flooded. The 3" Ø PVC protrusion in the side yard was missing its cap. As a result the main sewage drainline from the house to the city drain has become clogged. This causes burping at first. Followed by flooding.

FYI

cr3

Try Hen's suggestion first. Put some 10% bleach in the overflow hole that leads to the cavity. I just cleaned one that was truly foul.

I think the vent pipe is open, if we are referring to the same vent (ie: on the downstream side of the trap between the sink and the toilet traps on the main vertical). I ran a heavy chain down the vertical vent pipe (from the roof of the house) and it was open.

<If the vent on the roof is clogged pressure builds up and can force the air around the trap in the sink.>

The other possibility is that the rushing water is creating enough of a vacuum to 'pull the traps', i.e. to empty the U-bend of water until the next time the sink is used. With an empty U-bend there is nothing to block the vapours coming out of the drain. As other posts have correctly indicated, it all points to inadequate venting of the stench pipe outside the building. One of the possibilities is a birds' nest on the top of the pipe, for example.

In many cases I have found the trap under the sink clogged with sludge that really put out a foul oder.

We have a basement bathroom that doesn't get much use. I get the same smell, but I run water in the sink it goes away, until I assume that the trap dries out again and lets sewer gas come up thru the sink.