Why Do My Drains Smell Like Rotten Eggs?

That awful rotten egg smell wafting from your drain isn’t just a nuisance; it’s a sign that something is off in your plumbing system. This unpleasant smell is often tied to hydrogen sulfide gas, which can come from bacteria, sewer gas leaks, or even issues with your water heater. While a temporary fix might mask the odor, the real solution depends on what’s causing it.

To help you determine a cause and solution, we’ll cover typical issues, including:

Below, we break down the most common culprits and explain why this stinky situation might need a plumber’s attention.

One of the most common answers to “Why do my drains smell like rotten eggs?” is bacteria growth right inside the drain itself. When food scraps, grease, or organic matter settle in the drain, they create the perfect home for anaerobic bacteria.

These stinky microbes thrive without oxygen and produce hydrogen sulfide gas, which has an unmistakable rotten egg odor. You can try flushing the drain with boiling water or a baking soda and vinegar mix, but if the smell lingers after cleaning, it’s time to bring in the professionals.

A more serious reason for “Why does my plumbing smell like rotten eggs?” is sewer gas sneaking into your home. Hydrogen sulfide from the main sewer line can leak through cracks, loose fittings, or faulty traps and make your drains stink.

Watch for signs like persistent and strong odors, slow drainage, or an unsettling gurgle from the pipes. Sewer gas can pose health risks with prolonged exposure. Sealing gaps and cracks and checking for loose fittings are essential maintenance tasks that might correct sewer gas leaks, but calling in a plumber for a full inspection is your safest bet.

Dry or unused P-traps might answer the question, “Why does my sink smell like rotten eggs?” especially if the odor comes from a rarely used fixture. A P-trap is that curved section of pipe under your sink designed to hold water and block sewer gases from flowing into your home.

However, if a drain hasn’t been used in a while, such as in guest bathrooms or vacation homes, the water can evaporate, leaving an open path for odors. Running water through the drain occasionally can help keep the trap sealed and the stink out.

If that rotten egg smell shows up mostly when you turn on the hot tap, the problem might be inside your water heater, not the drain. Some bacteria can react with the anode rod and naturally occurring sulfate in the water, creating smelly hydrogen sulfide gas.

This gas makes your water smell like sulfur, even though your plumbing is fine. Flushing the water tank or replacing the anode rod might help, but a licensed technician can inspect it and run a water quality test.

If you’re still asking, “Why do my drains smell like rotten eggs?” after cleaning the surface, a hidden clog or venting issue might be to blame. Deep clogs and blocked vent pipes can make even the cleanest drains smell foul.

When the airflow is disrupted, like with a blocked vent, sewer gases can back up and escape through your fixtures instead of venting safely outside. Likewise, trapped debris from a clog can cause a lingering smell. Schedule a camera inspection or professional drain cleaning to clear things up for good.