What Is the Cause of a Moldy Smell When Running Water Down the Sink?

Bacteria and Fungus

• A drain is a dark and damp location that provides the perfect spot for fungus growth such as mold and mildew. In addition, discarded food and dirty water that flows into the drain will increase the chance of bacteria growth. Both fungus and bacteria will cause a musty smell in drains. No matter what the cause, removing the smell and the odor-causing problem requires only a few inexpensive items.

Boiling Water

• Boiling water will kill bacteria growing in drains while removing odors. In addition, the boiling water will help clean and clear the drain. After you've brought a pot of water to a boil, carefully pour it down the drain. Use oven mitts to protect your hands when moving the pot from the stove. You can use the boiling water as often as needed or in conjunction with other methods.

White Vinegar

• A natural liquid that removes odors, white vinegar will clean your drains while killing fungus -- such as mold and mildew. Pour 1 to 2 cups of white vinegar into the drain and wait for 30 minutes. This allows the vinegar enough time to eliminate the odors and get rid of the fungus. After the allotted time has passed, flush the drain for several minutes with hot water. To keep odors and fungus at bay, repeat the process once a month.

Baking Soda

• The naturally abrasive baking soda will not only scrub the drains clean but will remove odors. Before pouring 1/2 cup of baking soda in the drain, run hot water in the drain for two to three minutes. Dump the baking soda in the drain and place the drain cover on. After 30 minutes, flush the drain clean with boiling water. Repeat the process if the odor remains.