The short answer
What Causes the Smell
The most common culprit is a dry P-trap. That curved pipe under your sink holds water to block sewer gases. If you haven't used that drain in a while, the water evaporates, and gases rise into your home. Running water for a minute can refill the trap and often solves the problem right away.
Another cause is buildup of soap scum, hair, and food particles inside the pipe. Bacteria break down that gunk and release hydrogen sulfide, which smells like rotten eggs. This is more likely in kitchen drains or bathroom sinks that get heavy use. A thorough cleaning with baking soda and vinegar, followed by hot water, can reduce the odor.
How to Check for a Clog
If the smell stays after you run water, there may be a partial clog. Water draining slowly is a sign that gunk has built up. You can try a plunger or a drain snake to clear it. Avoid chemical cleaners that can damage pipes, especially if you have older plumbing.
If the clog is deep or you notice water backing up, that's a bigger issue. Standing water from an overflow can soak into walls and floors. In that case, you might need help from local water damage pros to handle the cleanup and drying. They can also check for hidden moisture that leads to mold.
- Run hot water down each drain for two minutes.
- Pour half a cup of baking soda, then half a cup of vinegar.
- Wait five minutes, then flush with boiling water.
- Check the P-trap under the sink for leaks or buildup.
- Use a drain snake if water drains slowly.
When It's More than the Drain
Sometimes the smell comes from the vent pipe on your roof. That pipe lets sewer gases escape outside. If it's blocked by leaves or a bird nest, gases can back up into your home. You can check for debris from the roof, but be careful on a ladder. If you're unsure, a roofer or plumber can inspect it.
A cracked or loose pipe joint can also let gases escape. Look under sinks and along exposed pipes for damp spots or stains. Water damage from a slow leak can rot wood and drywall over time. If you find moisture, turn off the water supply and call a plumber to fix the leak before it worsens.
Health and Safety Notes
Hydrogen sulfide gas is unpleasant and can irritate your eyes, nose, and throat. In high amounts, it can cause headaches or dizziness. If you feel unwell from the smell, open windows and leave the room. See a doctor if symptoms persist.
The smell itself isn't usually a health emergency, but it can signal a plumbing problem. If you have asthma or respiratory issues, avoid breathing the gas for long periods. Running fans and opening windows can help ventilate the space while you fix the cause.
When to Call a Pro
If cleaning and running water don't solve the smell, you may have a hidden issue like a broken pipe or a sewer line problem. A plumber can inspect the pipes and make repairs. If water damage has occurred from a leak or overflow, local water damage pros can extract water and dry out affected areas.
Water damage from a slow leak can lead to mold and structural rot. The pros use moisture meters and drying equipment to find hidden dampness. They can also remove damaged drywall or flooring if needed. For this type of work, you might want to look at water damage inspection or structural drying services.
Policies vary, and your insurer decides what is covered.
- The smell persists after cleaning and running water.
- You notice water stains on ceilings or walls.
- Drain water backs up or overflows.
- You suspect a broken pipe under the floor.
- You see mold growing near the drain.
Talk to someone now
Water keeps spreading into floors and walls, so it is worth acting early. Calls are answered 24/7.
Call Now (617) 404-2753Frequently asked questions
Is a rotten egg smell dangerous?
In small amounts, hydrogen sulfide is mostly an irritant. It can cause headaches or nausea if you breathe it for a long time. Open windows and leave the room if you feel unwell. If symptoms continue, see a doctor. The smell usually means a plumbing fix is needed, not a health crisis.
Will baking soda and vinegar fix it?
Often yes, for mild buildup. The fizzing action helps loosen gunk, and hot water flushes it away. It's a safe first step. But if the smell comes from a dry P-trap or a vent pipe issue, baking soda won't help. Run water first to rule out the P-trap.
Can I use bleach to get rid of the smell?
Bleach can kill bacteria, but it can also damage pipes if overused. It may not fix the root cause, like a dry trap or a clog. Try gentler methods first. If the smell persists, a plumber can identify what's really going on.