Water going down the drains in your kitchens and bathrooms can contain things in it that can build up over time or leave drains smelling badly. Bleach is a powerful disinfectant and can be used to kill mold, mildew and bacteria that may be inside your drains and contributing to a foul odor. Most times, the use of bleach is unwarranted and can be dangerous. But, if you do wish to clean your drains with bleach it is an easy task.
Pour a half a cup of bleach down the drain.
Allow the bleach to sit in the drain for three to five minutes.
Flush the drain with hot water for three minutes.