Why does my drain smell like rotten eggs?

Rotten egg smell from your drain is almost always caused by hydrogen sulfide gas, which occurs when organic matter decomposes in your plumbing system or when certain bacteria grow in stagnant water.

The most common culprit is your P-trap running dry. Every drain has a curved pipe section called a P-trap that holds water to block sewer gases from entering your home. If a sink, floor drain, or shower hasn't been used for weeks, this water barrier evaporates and allows smelly sewer gases to rise up through the drain. This is especially common in basement floor drains, guest bathroom sinks, or utility room drains that see infrequent use.

Biofilm buildup is another frequent cause, particularly in kitchen sinks and bathroom drains. Food particles, soap scum, hair, and other organic matter can accumulate in your drain pipes, creating a breeding ground for sulfur-producing bacteria. This slimy biofilm not only smells terrible but can also slow your drainage over time.

In Ottawa homes, water heater issues can also cause rotten egg smells, especially if you have an older electric water heater. The magnesium anode rod in your tank can react with sulfur bacteria in the water, creating hydrogen sulfide gas that comes through your hot water taps.

Start with the simple fix: run water in all your drains for 30 seconds to refill any dry P-traps. For persistent odors, try pouring a cup of baking soda followed by white vinegar down the drain, let it sit for 15 minutes, then flush with hot water. However, avoid chemical drain cleaners as they can damage pipes and don't address the root cause.

If the smell persists after these steps, or if multiple drains smell simultaneously, you may have a more serious issue like a damaged sewer line, blocked vent stack, or water heater problem that requires professional attention. For persistent drain odors in your Ottawa home, consider having a licensed plumber perform a camera inspection to identify the exact source and provide a lasting solution.