house smells like sewer when it rains

The Reason Your House Smells Like Sewer When it Rains

The Reason Your House Smells Like Sewer When it Rains

It’s happened to all of us at least once — you wake up on a drizzly morning or walk into your home after driving on a rainy day and something doesn’t smell quite right. Instead of a fresh, clean, natural scent, your house smells like a sewer when it rains. For some reason, you’re struck by a pungent odor that reminds you of a sewer backing up.

What’s going on? Why does your house smell like a sewer? We’re exploring possible causes, fixes and prevention tips below.

My House Smells Like a Sewer When It Rains! What’s Going On?

A sewer smell in your house can be extremely irritating, especially if there’s no apparent reason for it. There are a few possible causes, and we’ll talk about each in more detail below.

Bacteria and Decomposing Waste

The first and most common cause of a sewer smell in your house is the bacteria and decomposing waste in the sewer system.

The composition of most sewers is a mixture of moisture, human waste and drainage, which can produce an extremely bad smell. The off-gassing can actually be toxic, which is why sewer systems are designed with sewer traps to cut off the escape of gas.

Residential toilets have a u-shaped sewer trap in their system where water accumulates, forming a barrier between the sewer gases and your home. If the trap is not properly sealed with sewer plugs or the plugs have come loose, the result will inevitably be escaped sewer gas — or, in other words, a terribly pungent smell.

Dried-Out Water Barrier

If your house smells like sewer when it rains, another possible culprit may be a dried-out water barrier in the sewer trap, which is usually caused by a lack of use.

If you have a fixture in your home that isn’t used very often, such as a bathroom shower in the basement, then the water barrier inside the sewer trap can dry out. The quickest way to fix this is to run some water from that fixture to fill the trap belly and recreate the water barrier.

Similarly, if a leak causes the seal in the toilet’s u-shaped trap to drain, then sewer gases can begin to rise. This, in turn, can cause the gas to escape and collect inside your home, which can seriously affect the health and well-being of your family.

Water and Pressure

When it rains, rainwater runoff has to go somewhere when it falls. Because of gravity, it will usually go to the lowest point it can, pouring into any available culvert or break in the tank. As the water collects, it takes up space, causing the gas to move upward to accommodate the increasing volume of water. That’s because the fumes have a lower density, so they’ll begin to come out of sewers and cause a bad smell in the process.

If You’re on a Septic Tank

If you’re on a septic tank and notice a foul odor inside your home when it rains, the cause may be any — or a combination — of the following reasons:

  • Raining often causes atmospheric pressure changes, which can lead to the air becoming heavy. As such, the methane gases typically found in the septic tank don’t flow through the vent as they normally would. Instead, they stay low to the ground, causing a foul smell similar to rotten eggs.
  • Cold temperatures can cause downdrafts from plumbing vent stacks. In this case, you will notice the odor varies during the day, especially if the weather is windy. If the odor tends to subside as temperatures go up, downdrafts are the most likely cause of that terrible sewer smell in your house.
  • If the septic tank is full, it can cause the pump to fail. As such, new wastewater will not come in to replace the old wastewater, producing a foul smell as a result.
  • A blocked venting system in the septic tank is another possible cause of a sewer smell in your house. This often happens if you’ve had work done on the home or to the landscaping, and the vents are no longer working properly. The result will be sewage gases that can’t escape from the wastewater, accumulating in your house instead and causing a foul smell.

Other Causes of a Sewer Smell in Your Home

  • Cracked pipes: Degraded, broken or cracked pipes can allow sewer gas to escape through them and into your home.
  • Leaks: Improperly placed pipes or vents can lead to leaks in your plumbing system, which in turn can cause sewer gas to escape inside your home. Similarly, sewer gas can also leak into your home if the vents are installed too close either to a window or to an air intake. In some cases, leaks from nearby septic systems can enter your home through cracks in the foundation.
  • Clogged drains: Drains are responsible for the transportation of toxic waste through the septic system. The most common cause of clogged drains is sewage backup caused by items that shouldn’t have been poured or flushed. If not addressed, the clog can continue to decompose and produce an extremely foul smell in your home.
  • Loose toilets: Toilets that aren’t tightly fitted to the sewer lines can cause gas leakage in your home.

Is Sewer Gas Dangerous?

Yes — breathing sewer gas is not healthy and can be, in fact, quite dangerous if not promptly addressed.

Sewer gas is actually a combination of various gases and compounds, including hydrogen sulfide, methane, ammonia and carbon dioxide. While sewer gas isn’t dangerous in small amounts, some of the gases found in its composition can greatly contribute to high-level toxicity.

Hydrogen sulfide: Research has shown that hydrogen sulfide can be toxic to the oxygen systems of the body. Hydrogen sulfide in high amounts can also cause adverse symptoms, organ damage and sometimes even death.

Ammonia may already be familiar to you as a compound often used in cleaning chemicals. It is especially reputed for its distinctive odor. Exposure to low levels of ammonia can cause eye, nose and throat irritation. At higher levels, this compound can cause organ damage or death.

Both methane and carbon dioxide are relatively nontoxic and harmless to humans. However, methane can become extremely flammable in large amounts. Since ammonia, too, is highly flammable, there is no question that sewer gas at higher levels can be a serious fire hazard.

What Are the Symptoms of Exposure to Sewer Gas?

The very first sign of sewer gas in your home is a foul odor — think rotten eggs or sewage backup. Depending on the levels of sewer gas present, you may experience a range of symptoms, including:

  • Headaches
  • Lightheadedness
  • Nausea
  • Vomiting
  • Fatigue
  • Dizziness
  • Poor concentration
  • Poor memory

If high levels of sewer gas leak into your home, you can expect much more serious symptoms, such as:

  • Loss of smell
  • Mouth, throat and lung irritation (caused by the high levels of ammonia)
  • Eye irritation
  • Pink eye
  • Seizures
  • Coma
  • Death

If you smell sewer gas in your home, you need to take action right away to avoid putting yourself and your family at risk. Left unaddressed, sewer gas can accumulate and cause serious long-term health issues.


How to Prevent Sewer Smell in Your House When It Rains

When it comes to addressing the foul smell of sewer gas in your home, it all starts with prevention. Here are three preventative measures you can take to stave off sewer gas leakage inside your home and avoid the resulting foul odor.

Make Sure Water Stays in the Sewer Trap(s)

Once you know the location of all plumbing traps in your home, you can make sure they stay at the correct water level so as to avoid dried-out water barriers. If there are any fixtures that you use very rarely or not at all, a good way to prevent the traps from drying out is to pour a few tablespoons of vegetable oil on top of the water to slow down evaporation.

Clean Out Your Drains

Clogged drains are incredibly common. From debris to hair to toys and all kinds of other objects, a lot of stuff can find its way into your drains. To avoid clogs in your drains, you should regularly remove drain stoppers and clean the debris off of them, then set them aside.

If you have a pipe waste cleaner, you can stick it down the drain and pull out all the debris inside. If not, you can simply bend a small hook at the end of a wire and use it to remove debris instead. You can repeat this a few times until there’s no more debris in the drain. At the end, flush the drain with 4-5 gallons of boiling water and replace the stopper(s).

Make Sure the Toilet Isn’t Loose

As we’ve already explained above, a loose toilet can not only cause leakage right onto the floor, but it can also let sewer gases escape inside your home. Have your toilets checked for any loose joints or bolts to ensure there is no way for the odor to accumulate in your home.

DIY Shower and Sink Drain Sewer Smell Removal

Sometimes, the cause of a sewage smell after rain can be addressed with simple solutions you can try yourself. If the smell seems to be coming from the drain of the shower or a sink, you can use a tried-and-tested DIY fix with baking soda and vinegar.

Step 1. Pour ¼ cup of baking soda into the affected drain.

Step 2. Add one cup of white vinegar.

Step 3. Let the mixture sit for 2-3 hours. You’ll want to keep the door to the bathroom or kitchen closed during this time.

Step 4. Slowly pour a gallon of boiling water down the drain and wait 15 minutes.

Step 5. Run cold water for 10 minutes to help thoroughly rinse the vinegar down.

Step 6. Pour 1/2 cup chlorine bleach into the drain and let it sit for another 2 hours. Keep the door closed like you did at step 3.

Step 7. Rinse the bleach with another gallon of hot water.

Step 8. Let cool water run for 10-15 minutes.

By now, most of the debris clogging your drain should have been removed. There should also be ample water standing in the U-shaped curve of the sewer trap.

Step 9. Lastly, pour about 4 ounces of mineral oil into the drain to slow down water evaporation and avoid dry plumbing. Plain cooking oil works wonders.

When to Call a Specialist Plumber

Unless you’re an experienced DIYer or have previously dealt with sewer gas odor before, you should never attempt to fix the issue yourself. Due to the potentially hazardous nature of the problem, it is best to call a specialist plumbing company to address it.

Best San Diego Leak Detection offers a range of expert plumbing services designed to pinpoint the exact cause of the sewer smell in your home and fix it in the shortest possible time with as little inconvenience to you as possible. We use a variety of tools to help us get the job done, including odor sniffing detection tools, an infrared thermal imaging camera and electronic surveying.

If your house smells like a sewer when it rains, Best San Diego Leak Detection can help solve the problem quickly and efficiently. Get in touch with us today to learn more!

January 20, 2020 Categories:

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