My kitchen sink, installed 6 months ago, has a musty smell. I believe it comes from the $500. Grohe faucet. The hole in the granite where the faucet comes up through seems to smell, and sometimes I think that when I turn on the water, a musty smell comes along with it. The water doesn't taste bad, or smell when in a drinking glass. It is not the disposal system. I have checked for dampness under sink, in crawl space under the house, and under granite countertop. I did put a cloth soaked in bleach around the faucet entry from the countertop, but that didn't fix it. I don't know what bleach does to absolute black "granite" anyway.

Was the drain changed? Is there a possibility that sewer odor can be escaping?