Why Your Drain Smells Like Rotten Eggs or Sewage (and How to Fix It)
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Why Your Drain Smells Like Rotten Eggs or Sewage (and How to Fix It)
Rotten egg or sewer smell from a drain? The most common causes — dry traps, buildup, venting and water heaters — and how to get rid of the odor for good.
A rotten-egg or sewage smell usually comes from a dry trap, buildup inside the drain, a blocked vent, a failed toilet wax ring, bacteria in the water heater (hot water only) or a cracked sewer pipe. Start by pouring water into unused drains.
A rotten-egg or sewage smell in your home is unpleasant — and it's a clue. Here's how to track it down.
1. A dry trap
Every drain has a curved trap that holds water and blocks sewer gas. If a drain isn't used — a basement floor drain, a guest shower, a laundry tub — the water evaporates and sewer gas comes right in.
Fix: Pour a few quarts of water down the drain. For floor drains that rarely get used, a little mineral oil on top slows evaporation. If the smell stops, you've found it.
2. Buildup inside the drain
Hair, soap, grease and food slowly rot inside drain lines and give off sulfur smells — especially in bathroom sinks and kitchen drains.
Fix: A professional drain cleaning removes the buildup, not just the smell.
3. Venting problems
Plumbing vents let sewer gas escape through the roof. If a vent is blocked — by a bird's nest, leaves or ice in winter — drains can gurgle and smell.
Fix: Clear the vent. If drains gurgle too, that's a strong sign.
4. A loose or failed wax ring
If the smell is around a toilet, the wax ring that seals it to the floor may have failed. You might also see a rocking toilet or water at the base.
Fix: Reset the toilet with a new seal.
5. Only the hot water smells
If the rotten-egg smell only comes from hot water, the problem is likely in the water heater: bacteria reacting with the anode rod.
Fix: Flush and disinfect the tank, and sometimes replace the anode rod with a different type. See water heater repair.
6. A cracked or broken sewer pipe
A persistent sewer smell in the basement — especially with damp spots or slow drains — can mean a cracked cast iron pipe or a broken joint below the floor.
Fix: A camera inspection finds it. Our $199 sewer camera inspection includes a full report and video.
Find the source room by room
- Basement: start with the floor drain and laundry tub traps, then look for cracked cast iron.
- Bathroom: check the toilet base, the sink overflow and any rarely used shower.
- Kitchen: clean the disposal and check under the sink for a loose trap or a missing vent.
- Whole house: a smell everywhere, especially with gurgling, points to a blocked roof vent or a main line problem.
Taking note of where and when the smell is strongest helps us find the cause faster.
When to call a plumber
Call ExpertPipe Rooter at (216) 203-6563 if:
- Refilling the trap doesn't stop the smell
- The odor is strong, constant or getting worse
- Drains also gurgle or run slowly
- There are damp spots near basement drain lines
We serve Cleveland's west side and western suburbs, including Lakewood, Parma, Westlake, Rocky River and North Olmsted.
Frequently asked questions
Why does my basement smell like sewage?
The most common cause is a dry floor drain trap letting sewer gas in. If adding water doesn't help, a cracked pipe or failed seal may be the source.
Why does only my hot water smell like rotten eggs?
Bacteria in the water heater can react with the anode rod and create a sulfur smell. Flushing and disinfecting the tank, and sometimes changing the anode rod, fixes it.
Is sewer gas dangerous?
Strong, persistent sewer gas isn't something to live with. It can cause headaches and nausea, and the source should be found and fixed.
Keep reading
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