House Smells Like Sewer After Rain? (7 Common Reasons)

Have you ever noticed an unpleasant sewer-like smell in your house after it rains?

This is a common problem that many homeowners face, and it can be quite frustrating to deal with.

The smell is unpleasant and may also point to a more serious issue with your house’s plumbing or sewage system.

Here are 7 reasons why your house may smell like sewer after rain:

1. Blocked Drains

One of the most prevalent reasons your home smells like sewage after a rainstorm is blocked drains.

A blocked drain can cause sewage backup in your pipes, creating an unpleasant odor. Causes of blocked drains can range from flushing inappropriate items down the toilet to a buildup of grease and food particles in the kitchen sink.

If you suspect a blocked drain is the cause of the smell in your house, there are a few things you can do.

Try using a plunger to clear the blockage. If that doesn’t work, you can use a drain snake or auger to remove the obstruction.

Another option is to use a chemical drain cleaner. When handling these products, it’s crucial to read the directions thoroughly, wear gloves, and use safety goggles.

Chemical drain cleaners can effectively remove clogs caused by hair, grease, and other organic matter.

However, they can also harm pipes and the environment, so using them sparingly and as a last resort is important.

In some cases, a blocked drain may require professional help to fix. A plumber can use specialized tools to clear the blockage and prevent it from happening again.

Address a blocked drain promptly to avoid further damage and potential health hazards.

Regular maintenance and proper disposal of waste can also help prevent future blockages.

2. Dry P-Trap

The P-trap is a curved pipe underneath your sinks, shower, and bathtub that prevents sewer gases from entering your home.

Additionally, the P-water trap seals off the drain, preventing the gases from entering your living area and causing a leak.

However, if the P-trap becomes dry, it can no longer block the sewer gases, creating an unpleasant smell.

This can happen if you haven’t used a particular sink or shower for a while, causing the water in the P-trap to evaporate.

To fix a dry P-trap, pour water down the drain to refill the trap. You can also clean the drain and help break up any buildup using vinegar and baking soda. If the smell persists, you may need to check the P-trap for any damage or replace it altogether.

Keeping your P-traps filled with water is a simple and effective way to prevent sewer smells from entering your home.

It’s also important to regularly clean your drains and dispose of any food, hair, or other debris properly to prevent blockages and buildup in your plumbing system.

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3. Sewer Line Issues

Sewer line issues can seriously cause sewer smells in your home after rain.

Your home’s sewer line is responsible for transporting wastewater from your home to the municipal sewer system. If there is a problem with the sewer line, such as a blockage or a break in the pipe, sewage can back up into your home and cause a foul odor.

Some common causes of sewer line issues include tree roots growing into the pipes, grease and other debris buildups, and pipe damage from shifting soil or freezing temperatures.

If you suspect a sewer line issue is the cause of the smell in your home, it’s crucial to contact a professional plumber immediately. A plumber can use specialized equipment to inspect the sewer line and identify any issues.

Depending on the extent of the problem, the plumber may need to repair or replace parts of the sewer line.

It’s important to be proactive in preventing sewer line issues by properly disposing of household waste, such as grease, oil, and food scraps, and avoiding inappropriate flushing of items down the toilet.

Regular maintenance of your plumbing system, including cleaning your drains and inspecting your pipes for damage, can also help prevent sewer line issues from developing.

4. Septic Tank Issues

If your home or building has a septic tank, septic tank issues can also cause a sewer smell.

Septic tanks are designed to hold and treat wastewater from your plumbing fixtures. Over time, sludge and scum can accumulate in the tank, reducing capacity and causing backups or overflows.

Septic tank issues can also occur if the tank is damaged or there is a drain field problem. Lack of maintenance, flushing non-biodegradable items down the toilet, or overuse of water can also cause septic tank issues.

So, to identify septic tank issues, look for signs of slow drains, gurgling sounds, sewage backups, or wet spots in your yard. You may also notice an unpleasant odor coming from your drains.

If you suspect a septic tank issue is the cause of the sewer smell, it’s important to call a professional septic tank service to assess the situation.

They can pump the septic tank to remove the accumulated sludge and scum and repair or replace damaged components. They can also install a new septic system if necessary.

5. Roof Vent Issues

Problems with the roof vent can also cause sewer odor in your home or building.

Roof vents allow sewer gases to escape from the plumbing system and vent to the outside. If these vents become blocked or damaged, sewer gases can escape into the building, leading to a sewer smell.

Sewer smells can also enter the building through the ventilation system in apartment buildings or shared homes. This can occur if the ventilation system is connected to the plumbing system.

It can also be due to a leak or damage in the ventilation system that allows sewer gases to enter the building.

To identify ventilation issues, look for signs of a sewer smell throughout the building or in specific areas, such as bathrooms or utility rooms. In these areas, you may also notice slow drains, gurgling sounds, or water backups.

To fix ventilation issues, it’s important to call a professional HVAC technician or plumber to assess the situation and provide a proper solution.

This may involve sealing or repairing leaks in the ventilation system or adding a trap to prevent sewer gases from entering the building.

6. Mold and Mildew

While sewer smell is commonly associated with issues in the plumbing system, mold and mildew can also cause a musty smell that can be confused with sewer smell.

In homes, damp or humid areas like basements, bathrooms, and laundry rooms can support mold growth and mildew, emitting an unpleasant odor. It is crucial to identify the source of the smell to properly address the issue.

To identify mold and mildew, look for signs of dampness, such as water stains, discoloration, or peeling paint. You may also notice a musty smell in specific areas of the home.

If the mold and mildew are severe, you may need a professional to remove them safely and prevent further damage to your home or health.

To remove mild cases of mold and mildew, clean and dry the affected areas thoroughly. This may involve using a mold and mildew cleaner and wiping down surfaces with bleach.

You should also consider using a dehumidifier to reduce moisture in the air. Finally, fix any leaks or water damage contributing to mold and mildew growth.

7. Dead Animals

Another less common but possible cause of sewer smell is the presence of dead animals in the plumbing or ventilation system.

This can occur if an animal becomes trapped in a pipe or vent and dies, releasing an unpleasant odor into the building. It is important to address this issue promptly as it can pose health risks and attract other pests.

Look for indications of a potent odor that persists for a long time and cannot be attributed to any other source to determine the presence of dead animals.

Additionally, if living animals are present, you might hear scratching or crawling sounds in the walls or ceilings. Contacting a reputable pest control or animal removal service to remove dead animals is extremely important.

They can locate the animal safely, remove it, clean and sanitize the affected area, and stop the spread of disease and odor.


Washington State Department – Signs of Septic System Failure

Forbes – Average Sewer Line Repair And Replacement Cost 2023

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