 When you're using another drain in the house, that's why I asked if you heard any noise, and let's just use a toilet as an example because that's usually what it is. You flush the toilet. The flush is fine. Sometimes it's a little slow. Sometimes it's not. You'll hear a little gurgling, and then you'll get an odor. And what's happening is in order for that flush to complete, it needs air because it's gravity.