never had an odor with us. I have changed methods over time. I put about a gallon of water in, with maybe an ounce of chemical. after a day i add the rest of the chemical. we always dump right after a drive so everything is still in motion. flush with enough water to rid the tank of any left over debris. You also may need to add to the dosage. most bottle say good for about a week, or less in hot weather. so add some to it. Try a few different things until you got it. every situation is different. Good Luck & Be Safe ! ! !