Plumbing Mysteries: Why Does My Shower Drain Smell Like (Eww!) Rotten Eggs?

Luxury spa amenities can be over the top these days from the $5,000 Evian Bath in Miami (featuring 1,000 bottles of the French mineral water!) to the $1,000 white caviar illuminating facial (fish eggs on your face!) in Beverly Hills but, thankfully, you can pamper yourself at home.

The perfect “spa night” at home will naturally feature bath salts or oils, mood lighting, candles, music, and your favorite comfy robe.

While barking dogs and screaming kids can wreck your spa moment, there is another unwanted guest that can put a damper on your evening: the smell of rotten eggs emanating from your shower drain.

That Smell is Trying to Tell You Something About Your Plumbing

While it might seem like an innocuous inconvenience, this funky odor can be more than just a hindrance to your bath night bliss; it can also signal potential plumbing issues that need attention.

“If your shower drain smells more like an expired egg than clean linens, that’s an issue that needs tackling. The truth is that there could be several reasons why a shower drain might smell like rotten eggs, from faulty plumbing to bacteria in the drain breaking down organic matter,” says This Old House.

Rotten Egg Smells Sets Off Alarm Bells … For a Reason!

Rotten egg smells set off the alarm bells in your brain for a good reason: for starters, gas companies inject a chemical called mercaptan into their supply so you can smell gas leaks, which, otherwise, would be odorless.

So, if that rotten egg smell is coming from a gas appliance or gas pipe, call your utility provider or local fire department immediately.

Even if the smell is coming from your shower drain, you need to act as one of the causes could be sewer gases entering your home because of damaged pipes or faulty seals.

The International Associated of Certified Home Inspectors (NACHI) says that sewer gases pose the following risks to building occupants:

  • Hydrogen sulfide poisoning: Hydrogen sulfide is an explosive and extremely toxic gas that can impair several different systems in the body at once, most notably the nervous system.

  • Asphyxiation: When sewer gases diffuse into household air, they gradually displace oxygen and suffocate occupants.

  • Fire or explosion: Methane and hydrogen sulfide are explosive components of sewer gas.

  • Odor: Hydrogen sulfide is responsible for sewer gas’s characteristic rotten-egg smell, which can be overbearing even at extremely low concentrations.

“If you suspect that any odors might be caused by sewer gases, contact a qualified plumber,” advises the NACHI.

P-What? Understanding Plumbing Lingo

Before we dive into the reasons behind your shower's stinky predicament, let's brush up on some essential plumbing terms that will help you navigate this world:

  • P-Trap: This is a curved section of pipe beneath your sink or shower that traps water to create a seal. It prevents sewer gases from wafting back up into your home. P-Traps are also known as U-Traps or drain traps. These traps are made of plastic or metal.

Misconception: Some homeowners think they have a problem if there is water in their P-Trap, but the device's job is to retain some water to prevent sewer gases from sneaking back up the drain system and out your shower or sink drain. When there is no water in your P-Trap, then you have a potential problem.

  • Anode: In water heaters, an anode rod is a sacrificial component that prevents rust and corrosion. Without it, you'd be showering in rust-colored water.

  • PVC Elbows: PVC (polyvinyl chloride) elbows are bendy plumbing components that connect pipes at angles. They help direct water flow in your plumbing system.

7 Reasons Your Shower Drain Smells Like Rotten Eggs

Now that you “speak plumber” let's uncover the reasons why your shower vent might smell like rotten eggs, and what the fix is for the problem:

  • The Culprit: Bacterial Buildup: Inside your P-Trap, warm, stagnant water can become a breeding ground for bacteria. These little critters release hydrogen sulfide gas, which smells like rotten eggs when it rises through your shower drain. This Old House says that when these microorganisms stick together they can create a slimy, mold-like biofilm.

The Fix: Pour some baking soda and vinegar down the drain to clean the area and clear out the bacteria. Run hot water afterward to flush out any remaining biofilm. If you do not want to DIY, you can opt for a standard drain cleaner.

  • The Sneaky Suspect: A Dried-Up P-Trap: If a shower or sink isn't used often (think guest bath), the water in the P-Trap can evaporate, breaking the seal that prevents sewer gas from entering your home.

The Fix: Run water in the unused shower or sink regularly to keep the P-Trap filled. It's like a little plumbing spa day! This Old House says the frequency of running the water in an unused bath depends on factors such as the home’s humidity level, the location of the drain, the time of year, and how often the drain is used. Every two weeks is a good rule of thumb.

  • The Sulfur Stinker: Water Heater Anode Reaction: In some cases, your water heater's anode rod can react with the water's chemistry, producing hydrogen sulfide gas. Remember, the anode’s role is to collect particles of iron, limestone, and other minerals in the water. Without your anode, your water heater would corrode quickly. When the anode starts to go, however, you may start to smell sulfur or rotten eggs in your water.

The Fix: If your water heater is the culprit, it might be time to replace the anode rod or it might be time to upgrade your water heater to a newer model. Consult a professional plumber for your options.

  • The Greasy Gang: Clogged Pipes: Grease and debris can accumulate in your pipes over time, creating a smelly clog.

The Fix: Try using a plumber's snake or a mixture of baking soda and vinegar to break down the clog. If that doesn't work, call in the experts.

  • The Invasive Invader: Sewer Gas Infiltration: In some cases, sewer gas can enter your plumbing system through damaged pipes or faulty seals. This Old Home says that cast-iron pipes or PVC elbows and joints are vulnerable to cracking and breaking. And that rotten egg smell? Might actually be coming from under the floor in your bathroom due to leaks from the damaged pipe.

The Fix: This one calls for a professional plumber to inspect your pipes and make necessary repairs. You may also need other remediation and remodeling work done if the leak from the cracked pipe has caused water damage to drywall and other building materials.

  • The Ventilation Vexation: Poor Ventilation: Inadequate ventilation in your plumbing system can trap odors and allow them to seep into your home. Plumbing drain systems have open vent pipes (typically found at the roof line). These vents allow fluids to exit your system, but they can be clogged by debris, bird’s nest, and other obstructions.

The Fix: Have a plumber inspect your plumbing vents to ensure they are properly functioning and not obstructed.

  • The Sulfur Surprise: Sulfur Water from a Well: If your home relies on well water, sulfur bacteria may be the source of that unpleasant smell. These bacteria thrive in oxygen-deficient environments, often found in well-water systems.

The Fix: Consider installing a well water treatment system to address sulfur bacteria and remove the rotten egg odor. Consult a water treatment professional to determine the best solution for your specific well water situation.

“One of these methods is bound to take your shower from eggy and stinky to fresh and clean. Though it may take trial and error in order to pinpoint the exact issue first, don’t give up as a solution to a shower drain free from odors may not be far off,” advises This Old Home.

Pilot Plumbing, operating in the Montgomery County and North Houston area, can help you eliminate the rotten egg smell in your shower drain and return your spa night to an evening of bliss.

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