Why Does My Kitchen Sink Drain Smell Like Rotten Eggs?

The U-shaped pipe under your sink, called a p-trap, holds water to block sewer gases. If a sink is rarely used, this water can evaporate, letting odors enter your home. A clog in the trap can also trap rotting food, which produces the sulfur smell. Running water down the drain weekly can keep the trap sealed and prevent the odor.

A partial clog often traps grease and food particles that decompose over time. This creates a breeding ground for bacteria that release hydrogen sulfide. The smell may be strongest when you first run water, as it disturbs the decaying material. A simple drain cleaning can often resolve this issue if the p-trap itself is the source.

Your home's plumbing system has vent pipes that allow sewer gases to escape outside through the roof. If these vents become blocked by leaves, a bird's nest, or ice, pressure can build up in the drains. This pressure can force sewer gases back into your home through the sink drain, carrying the rotten egg smell with it.

You might notice gurgling sounds from other drains when this happens. A blocked vent is not a DIY fix and requires a plumber to safely clear it. They can inspect the roof vent line to remove any obstruction and restore proper airflow, which should eliminate the odor coming from your drains.

Start by pouring a mixture of baking soda and vinegar down the drain, followed by hot water, to break up minor clogs and biofilm. If the smell persists, inspect the p-trap for clogs or leaks. You can remove and clean the p-trap yourself, wearing gloves, to clear out any trapped debris causing the odor.

If simple cleaning does not work, the issue may be deeper in the pipes or related to a vent. At this point, call a plumber. They can perform a camera inspection of your drain lines to identify cracks, blockages, or a failing sewer line that could be the source of the gas.