I have had a problem with a very bad odor in my kitchen sink drain since the weather got warm. My home is new and is a manufactured home in a park. I have used gel drain openers followed by boiling water and when that did not work I used a box of baking soda, 1cup of salt and 1 cup of vinegar, let it fizz for 15 minutes and then flush with 4 qts. Of boiling water. The fix is only good for a few days, then the smell returns. I sure do need some good advice. PS. The smell comes mostly from the disposal side of the sink and I do have a dishwasher.