There actually is a p-trap, which works 95% of the time, just not when the kitchen faucet is run, and occasionally it will fail just by itself (I'm figuring it just empties through evaporation).
A picture:
Actually I did, I don't think the pipe was completely clogged, just mostly. I can't remember precisely but I think it was even worse.
Are you saying that there is a p-trap under the floor or in the wall?
Because that grey curved pipe I see on the left is not a p-trap and won't keep the odor out. The curved part should hang toward the floor, not swing on the side.
You can see an example here:
Looks to me like it does curve toward the floor. And while it's a little shallow, it would probably work fine if it were vented on the downstream side.
(by vented, I mean connected to a vent stack, not poking a hole in it.)
And you're right, sorry. I was seeing a floor behind the pipe but that's a wall. My bad. I agree, that should work.
Perhaps the OP could divert the AC drain to a large container for a few days and make sure to close off the part going in the wall. If the odor disappears the pipe is the problem.
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