What Sewer Gas Smells Like and How to Remove It From Your House

Sewer gas refers to the mixture of toxic gases that can accumulate within household plumbing and sewer systems. Exposure to sewer gas poses significant health risks, so it’s important to know how to recognize it and remove it from your home. In this comprehensive guide, we’ll cover everything you need to know about sewer gas smells and removal.

What Causes Sewer Gas Buildup

Sewer gas forms when bacteria break down waste materials in sewer pipes and drains. The bacteria release hydrogen sulfide gas, which is responsible for the rotten egg smell commonly associated with sewer gas.

Here are some of the main causes of sewer gas buildup in homes:

  • Clogged or damaged drains or sewer lines – Clogs prevent waste from properly draining, allowing gas-producing bacteria to thrive. Cracks and holes also provide an escape route for sewer gas to enter the home.
  • Dry drain traps – Drain traps hold water to block sewer gas from passing through plumbing fixtures. If the water evaporates, gases can escape through drains.
  • Backflow of sewage – During heavy rain or flooding, sewer lines can get overwhelmed and sewage can back up into the house through drain pipes. This brings sewer gas along with it.
  • Improperly installed plumbing – Incorrect slope or unsealed connections in drain lines allows gases to leak through. Venting issues also prevent gases from properly escaping outdoors.
  • Empty or unused drains – Stagnant water in rarely used drains, sinks, showers or toilets can start emitting sewer gases after a while.

Recognizing the Smell of Sewer Gas

Being able to identify the odor of sewer gas is key to detecting a problem early and avoiding prolonged exposure. Here’s how to recognize some of the most common sewer gas smells:

  • Rotten eggs – The classic sewer gas smell is described as rotten egg or sulfur. This is caused by hydrogen sulfide gas. The strength of the odor depends on the concentration of gas.
  • Decayed organic matter – Sewer gas may smell like decomposing vegetables, compost or rotting garbage. This is caused by organic waste breaking down.
  • Fishy or ammonia-like – A fishy or urine-like smell may indicate liquid sewage backup containing nitrogen.
  • Mothballs – A chemical odor like mothballs or pesticides could mean dangerously high levels of methane or hydrogen sulfide gas. This signals a serious hazard.
  • Fecal or “poop” smell – The actual smell of human or animal waste may be present if solid matter is accumulating and decomposing in clogged drains.
  • Musty or earthy – Some describe sewer gas as musty, moldy or having an earthy, muddy smell. This may indicate organic buildup.

Sewer gas odors are often most noticeable in bathrooms or basements near floor drains. The smell may only occur when a fixture is run or drained. Vents on the roof can sometimes release small amounts of odor outdoors as well. Any sewer gas smell in your home should be promptly addressed.

Health Dangers of Sewer Gas Exposure

Exposure to sewer gas can present both short-term and long-term health risks. Here are some of the main ways that sewer gas affects human health:

  • Headaches, dizziness, and nausea – Hydrogen sulfide gas causes irritation and symptoms like headaches, lightheadedness, nausea, dizziness and fatigue.
  • Eye and respiratory irritation – Sewer gas can aggravate asthma and allergies. It may cause sore throat, coughing, watery eyes and difficulty breathing.
  • Carbon monoxide poisoning – High levels of methane gas can displace oxygen levels and lead to carbon monoxide poisoning with symptoms like chest pain, vomiting and loss of consciousness.
  • Explosion hazard – At very high concentrations, sewer gas like methane and hydrogen sulfide is explosive and extremely dangerous.
  • Long-term organ damage – Repeated exposure to sewer gas has been linked to problems like Chronic Obstructive Pulmonary Disease and increased cancer risk. Pregnant women and infants may be at higher risk from toxins that affect development.
  • Death – At high enough concentrations, sewer gas can be immediately fatal due to asphyxiation, poisoning or explosion hazard. Low oxygen environments are especially dangerous.

Sewer gas symptoms usually go away once the exposure ends. However, long-term sewer gas issues must be corrected to avoid catastrophic health impacts or death.

Detecting Sewer Gas in the Home

Since sewer gas exposure poses a serious health hazard, it’s important to identify and fix any sources of gas in the home. Here are some ways to check for sewer gas leaks:

  • Use your nose – Simply smelling for odors around sinks, tubs, shower drains and other fixtures. Odor near floor drains is a red flag.
  • Listen for gurgling sounds – Drain traps drying out may make a bubbly, gurgling noise as sewer gases escape.
  • Check plumbing vents – Walk around your roof and look for any vent pipes emitting foul odors. Nearby plants dying can also indicate venting issues.
  • Conduct a smoke test – Some plumbers can pump non-toxic smoke into your plumbing system and pinpoint where it escapes.
  • Use a gas detector – For large homes, specialized gas detectors can sniff out sewer gas leaks. Hydrogen sulfide detectors are available for purchase.
  • Look for signs of damage – Check for any sagging drain pipes, leaky joints, or settling around the foundation which may compromise plumbing.

Promptly investigating any suspicious odors or unusual plumbing conditions can help identify health hazards before the problem worsens. Call a professional plumber if you have difficulty determining the source.

How to Remove Sewer Gas Smell from Your House

If your house has sewer gas odors, taking steps to remove the gas and prevent it from entering in the first place is crucial. Here are some tips to eliminate sewer smell in your home:

Immediate Steps to Remove Odor

  • Open windows – Air out affected rooms to rapidly reduce odor. Turn on bathroom fans and range hoods to ventilate.
  • Set up fans – Place box fans facing outwards in windows to push gas outdoors.
  • Seal floor drains – Use plastic sheeting, duct tape or plugs to temporarily seal drains.
  • Pour water – Run sinks, tubs and showers to fill drain traps and block gases. 1-2 cups of water added weekly can also maintain traps.
  • Spray neutralizer – Products like Odoban or air fresheners can chemically neutralize some odors short-term.
  • Drain cleaners – Pour enzyme cleaners or baking soda and vinegar into drains to help break down waste.

Identifying and Fixing the Source

Determining and repairing the underlying cause of sewer gas entry is the only real solution. This usually requires a professional plumber. They can:

  • Inspect and clear clogs – Using augers, snakes and high-pressure jets to remove obstructions.
  • Fix pipe and drain damage – Replacing broken sections of pipe or seals to prevent gas leaks.
  • Install backflow valves – Adding a backflow prevention device to block sewage back-ups.
  • Repair venting – Adjusting or adding vent lines so gas can escape outside.
  • Update fixtures – Replacing aged, faulty pipes, traps and connections.
  • Level out floor drains – Adjusting drain slope to allow complete drainage and prevent stagnation.
  • Treat root intrusion – Removing roots that grow into and break pipes.

Preventative Measures

After addressing any underlying issues, some basic maintenance can help prevent recurrence of sewer gas odors:

  • Regular drain cleaning – Use enzyme cleaners monthly to reduce buildup.
  • Pour water in unused drains – Add water weekly to fill traps in rarely used plumbing.
  • Check vents – Ensure vent lines stay clear of blockages from insects or debris.
  • Update old plumbing – Have vintage pipe and drain materials replaced with modern PVC.
  • Install cleanouts – Cleanouts provide plumber access to clear stubborn drain clogs.
  • Consider gasketed covers – Airtight, gasketed drain covers further block sewer gas escape.

Addressing sewer gas promptly is critical for health and safety. With some vigilance and plumbing maintenance, you can avoid encountering unpleasant and dangerous sewer gas within your home. Contact a professional plumber immediately if odors persist after attempting DIY remedies.

FAQs About Sewer Gas Smells and Removal

What does sewer gas smell like in bathroom?

In bathrooms, sewer gas most commonly smells like rotten eggs, decayed organic matter, or musty/moldy odors coming from sink, shower and tub drains. The smell may be strongest when water goes down the drain. Bathrooms are ground zero for sewer gas because plumbing fixtures drain directly into sewer gas-prone areas.

Why does my bathroom smell like poop?

A straight-up fecal odor in your bathroom likely means sewage solids or waste-water is collecting in a nearby drainage pipe orfixture trap. Clogs in the main sewer line can back up wastes into drain lines. Leaks also allow gases from decomposing matter to escape into the room. Call a plumber to diagnose and clear the blockage.

How dangerous is sewer gas?

Exposure to even small amounts of sewer gas like hydrogen sulfide can cause headaches, breathing issues, dizziness and nausea. Higher concentrations—which may occur in confined spaces around large leaks—can cause life-threatening oxygen depletion, explosion hazards, and long-term organ damage. Children and the elderly are at highest risk.

Can sewer gas make you sick?

Yes, sewer gas exposure is linked to a range of acute and chronic health effects. Short-term illness can include sore throat, eye irritation, respiratory problems and headaches. Long-term effects may include increased cancer risk, lung disease, and neurological impacts from toxins. Hazards are worst with frequent or prolonged exposure.

How do you fix a smelly bathroom drain?

To stop bad smells from the bathroom drain, first try pouring a few cups of water to fill the drain trap. If the smell persists, use baking soda and vinegar to break up organic material. For stubborn odors, use an enzyme based drain cleaner monthly. A plumber can also snake the drain or inspect it for cracks allowing sewer gas to leak in. Proper venting is key to keeping bathroom drains smelling fresh.

Why does my basement smell like poop sometimes?

A fecal waste odor in your basement likely means sewer gases are entering from floor drains, pipes or sump pumps connected to the main sewer line. Gases can leak through tiny cracks or dry drain traps. Make sure all basement drains have water in the traps and use plastic sheeting to temporarily block the drains when not in use. Call a plumber to locate and seal any pipe or drain defects if odors persist. Proper venting to outdoors is also critical.

How do you find a sewer gas leak in your home?

Start by sniffing around plumbing fixtures and floor drains for any foul odors. Gurgling sounds, high humidity or musty smells near drains indicates sewer gas may be leaking in. Run water through fixtures to see if any drain traps were dry. Conduct a smoke test by pumping non-toxic smoke into plumbing pipes and looking for where it escapes. Use a gas detector to pick up on hydrogen sulfide or methane leaks. Also check vent pipes on the roof for odors. Calling a plumber for a thorough inspection is safest if you suspect any leak.

Will sewer gas eventually go away?

Simply waiting for sewer gas to dissipate is not safe or recommended. The underlying issue allowing gases to leak into the home, such as cracked pipes or missing venting, must be repaired to stop odors long-term. Sewer gases contain toxic substances that can quickly cause health impacts with continued exposure. Eliminating the source also reduces explosion risk from methane buildup. Never ignore persistent sewer gas smells indoors.

How long does it take for sewer gas to dissipate?

When a fixture or drain trap dries out, the initial release of sewer gas may naturally dissipate within a day or two after replenishing the water seal. However, serious leaks from damaged plumbing will allow persistent gas intrusion that does not go away on its own. Foul odors lingering more than a day or two almost always indicate an underlying defect needs repair by a professional plumber. Ventilation can help speed the removal of odors in the short term.

Can sealing basement floor drains stop sewer gas?

Sealing floor drains may help slow sewer gas odors temporarily, but it is not a permanent solution on its own. Water or debris can still enter the sealed drain and require removal later. Floor drain traps also must be kept filled to prevent gases from passing through. For long-term control of sewer gas, any pipe damage, clogs or venting issues must be fully resolved first. Updated plumbing materials and proper drainage slope are also important preventative measures.


In summary, sewer gas leakage into homes creates a hazardous situation that requires immediate attention. Recognizing the sulfur, rotten egg or musty odors associated with sewer gas is key to identifying leaks early. Exposure can lead to health impacts ranging from headache and nausea to life-threatening conditions. Professional plumbing repairs are required to solve the underlying issue allowing gases to enter from damaged or improperly installed pipes and drains. Strict preventative maintenance, like frequent drain cleaning and updated plumbing materials, can also help reduce risks. Addressing sewer gas promptly is critical to protect both health and home. With the right plumber’s help, your house can stay sewer gas-free for good.