On 3 Feb 2007 13:06:43 -0800, wrote:

On Feb 3, 4:52 pm, Richard J Kinch wrote:
When I run the kitchen sink, and the AC kicks on, I get a bad smell
throughout the apartment. If I run the kitchen sink, and the AC is
off, I get the same smell, just much fainter. I put a cork in the
pipe where it enters the drain pan, and run the kitchen sink and AC,
and got no smell at all. So I'm guessing it's coming from the drain
line. It's of varying strength, and I don't know if it's sewer gas or
not, but it's definitely unpleasant.

Do you have a trap in the condensate line? Should be there. Otherwise
you're pushing air out through it (traps dust which promotes clogging) or
suctioning sewer gas in (yuk).


Yep, there's a trap, though not an especially large one. I posted a
pic of it at:
http://i9.photobucket.com/albums/a93...r/AC_drain.jpg

I'm trying to figure out if there's a way to somehow intentionally
empty the trap so I can see if the smell comes without having to run
the kitchen sink.


I'm trying to make some sense of what I'm seeing in your photo.
Perhaps you can clarify some items.

What is the curved black line which comes from above and looks to
connect to left side of the trap?

I think I also see, above the left end of the trap, an automatic vent.
If so, these are prone to failure and often cause a sewer gas odor
problem. I'm puzzled why it is in this location, as it should be on
the sewer side of the trap.

I'm in the northeast, and overhead AC systems may be different in FL.
Here, when systems which are mounted above finished spaces, they are
normally equipped with two completely separate drain lines. The first
is the normal condensate line. The second is a backup line connected
to a drip tray placed under the AC unit incase the first line becomes
blocked.

My hypothesis, without seeing the rest of the plumbing is the
following:

1) The roof vent pipe for the kitchen sink is obstructed, perhaps by a
bird or bees nest, or?? (The kitchen sink may not even have a proper
vent - the quality of the plumbing in your photo does exactly give me
a good feeling that it is plumbed correctly.)

2) When you run water in the kitchen sink, it is drawing vent air
through the automatic vent by your AC unit. It will also suck all the
water out of the trap on the AC's condensate line.

3) Now you have a clear path from the sewer line right into your AC's
intake air suction side.

4) Honey, what's that smell?! :-(

....gary