When an aroma of onions seeps out of your shower drain, it can quickly fill the bathroom with the over-powering odor. This odor will turn the shower -- as well as surrounding areas -- into a stinky mess. Once you figure out the cause of the onion odor, you can eliminate it and keep it from returning.
The onion smell coming from the drain may be due to hair, grime and grease buildup in the drain. When you shower, the dirt, grease and grime from your body go down the drain and can become trapped, causing clogs and odors. Another reason for the onion aroma may be a buildup of bacteria. Whether from grime buildup or bacteria, removing the smell is the same process. However, the onion odor may not be coming from the drain at all; the source could be the water.
Remove the Drain Odor
Several methods will dissolve any clogs -- such as hair, grease and grime -- in the drain, along with the odor caused by the clogs and the bacteria growing in the shower drain. You can use each method alone or in conjunction with each other to maximize odor removal. Plain boiling water poured down the drain will help soften up any clogs and clean the drain. Then pour white vinegar or baking soda down the drain and wait 30 minutes before flushing the shower drain clean with hot running water.
Remove the Water Odor
Over time, the water inside the water heater can develop unpleasant odors. To alleviate these odors, drain the hot water heater and change the anode rod. Anode rods protect the hot water tank from corrosion and can develop an unpleasant odor that transfers to the water. Refer to your hot water tank owner's manual for the specific instructions on how to replace the anode rods and drain the tank for your make and model of water heater.
The best defense against a smelly shower drain is prevention. Once a week, pour white vinegar down the drain in the shower and let it sit for 30 minutes before rinsing the drain clean with hot, running water. Regular use of white vinegar will keep future clogs at bay while killing fungus -- such as mold and mildew -- and eliminating odors.