Why Does My Shower Drain Smell Like Rotten Eggs?
Clogged Drain
A common cause of a rotten egg smell from a shower drain is a clog. Hair, soap scum, shampoo, conditioner, dirt, and oil can accumulate in the drain, creating a breeding ground for bacteria. As bacteria feed on this waste, they release hydrogen sulfide gas, which has a pungent odor like rotten eggs.
Dry or Dirty P-Trap
The P-trap is a U-shaped section of pipe beneath the drain that holds water to prevent sewer gases from escaping. If the P-trap is dry or dirty, it can’t effectively block these gases, leading to a rotten egg smell.
Leaking Pipes
If the drain pipes behind the walls or under the floor are leaking, waste can seep into the insulation and release pungent gases. Even if the gas is trapped by water in the P-trap, the area behind the wall or under the floor can become a breeding ground for bacteria and mold, further contributing to the odor.
Biofilm Buildup
Biofilm is a colony of bacteria and their waste that forms a slimy substance in drains and other moist areas. It thrives on soap scum, hair, and other debris. Biofilm can develop around the drain lip, in the P-trap, or on other surfaces in the bathroom, releasing a rotten egg smell as the bacteria break down waste.
Contaminated Water
In rare cases, the water itself can be the source of the rotten egg smell. Raw sewage may have seeped into the home’s water supply, or the water may have high levels of sulfate ions. Sulfate ions react with the anode rod in the water heater, producing hydrogen sulfide gas.
Anode Rod Reaction
The anode rod in a water heater is designed to protect the tank from corrosion. However, if the water contains sulfate ions, they can react with the anode rod, releasing hydrogen sulfide gas and causing a rotten egg smell, especially in hot water.
How to Fix a Shower Drain That Smells Like Rotten Eggs
Clogged Drain:
- Use a drain snake to remove large clogs.
- Pour baking soda down the drain, followed by vinegar, and cover the drain to allow the reaction to clear the clog.
Dry or Dirty P-Trap:
- Run water into the drain to fill up the P-trap.
- If there’s a blocked or broken drainage vent, call a plumber to clear or repair it.
- Pour baking soda and vinegar into the drain to disinfect and deodorize the P-trap.
Leaking Pipes:
- If you suspect a leak, repair it yourself if possible or contact a plumber.
- Check for damage to insulation, drywall, or flooring and repair as needed.
Biofilm Buildup:
- Clean the drain and affected areas with a bathroom cleaning solution.
- Use a vinegar and baking soda mixture for a quick DIY remedy.
- Clean the bathroom regularly to prevent biofilm formation.
Contaminated Water:
- Send a water sample to a lab for testing to identify the source of the smell.
- Stop drinking the water until the test results are back.
- If the water has high sulfate levels, install an iron filter to remove excess ions.
Anode Rod Reaction:
- Replace the magnesium anode rod with an aluminum rod.
- Remove the anode rod altogether (but this eliminates corrosion protection).
- Install an iron filter before the water enters the water heater to prevent the reaction.
