We have an odor in our kitchen that is driving us crazy! It is a sour odor, sometimes smells like a chemical of some sort. We moved into this house about a month ago, the house is about two years old. We thought it might be the air admittance valve, so we had a plumber replace it. The odor persists (and the plumber says the odor is NOT sewer gas). We can smell it through the dishwasher...which we removed as an experiment to see if that was the culprit. Still stinks. You can only smell it under the sink, not from above. Any ideas?