House Smells Like Rotten Eggs? Is It a Gas Leak or Something Else?
A rotten egg smell in your house is alarming. It could be a gas leak, a dead animal, a drain problem, or a sewer issue. Here is how to tell.
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If You Suspect a Gas Leak: Act Immediately
Natural gas is odorless, but utility companies add mercaptan, a chemical with a strong rotten egg smell, so you can detect leaks. If the smell is strong and pervasive throughout the house, do NOT flip any light switches, do NOT use your phone inside, do NOT light matches or candles. Leave the house immediately with all family members and pets. Call your gas company emergency line or 911 from outside or a neighbor house. Gas leaks can cause explosions. This is not an overreaction — gas company emergency response is free and they would rather check a false alarm than respond to an explosion.
If the Smell Is Near a Drain: Sewer Gas
The most common cause of rotten egg smell indoors is sewer gas coming up through dry P-traps. Every drain in your house has a U-shaped pipe called a P-trap that holds water to block sewer gas from entering your home. If a drain has not been used in weeks or months — a guest bathroom, floor drain in the basement, utility sink — the water in the trap evaporates and sewer gas enters. The fix is simple: run water in every drain for 30 seconds to refill the P-traps. The smell should clear within an hour.
If the Smell Is in Hot Water Only: Water Heater
If the rotten egg smell only occurs when running hot water, the anode rod in your water heater is reacting with bacteria in the tank. The anode rod is a metal bar inside the tank that prevents corrosion. When it degrades, it can produce hydrogen sulfide gas, which smells like rotten eggs. Flushing the water heater and replacing the magnesium anode rod with an aluminum-zinc rod (about 25 dollars) usually eliminates the smell. You can also add hydrogen peroxide to the tank to kill the bacteria.
Other Possible Causes
A dead animal in a wall, attic, or crawl space produces a smell that worsens over time and is localized to one area. Drywall that was manufactured with defective materials (common in homes built with Chinese drywall between 2001 and 2009) can emit sulfur gas. Certain types of bacteria in sink drains produce hydrogen sulfide — clean the drain with baking soda and vinegar followed by boiling water. If you cannot identify the source, call a plumber to inspect your drains and a gas company to test for leaks.
