Why does my house smell like sewage after it rains?

The sewage smell in your house after it rains is most likely caused by a backup or failure in your plumbing system or sewer line, leading to sewer gases being pushed back into your home.

 

Understanding Sewer Gases

  Sewer gases are byproducts of the decomposition of waste. They contain compounds such as hydrogen sulfide, which gives off a distinctive rotten egg or sewage odor. These gases are normally vented out of your house through plumbing vents. When issues occur, such as blockages or poor ventilation, these gases can accumulate inside your home.

 

How Rain Can Trigger These Issues

  Rain increases water volume that flows into drainage systems. When heavy rain occurs:

• Water can saturate the ground, causing the sewer lines to become overwhelmed or back up, forcing gases back through the pipes.
• Clogged or improperly functioning storm drains can force excess water into your sewer system, leading to pressure buildup that displaces the gases inside your home.
• The water may also find its way into small cracks or faulty seals around drains and pipes, carrying sewer smells along with it.

 

Plumbing Factors to Consider

  Several plumbing issues could contribute to this problem:

• Venting problems: If the vent pipes that allow sewer gases to escape are blocked, these gases may re-enter your living space.
• Trapped air or water in P-traps: These are the curved pipes under sinks and other fixtures designed to hold water and block gases. If they dry out or are siphoned out during a heavy rainfall, the barrier is lost.
• Septic system problems: For houses not connected to a municipal sewage system, a malfunctioning septic tank can leak or backflow, releasing smells into the house.

 

Structural and Environmental Considerations

  Sometimes the layout of your property or the natural ground conditions around your home can amplify the problem:

• Groundwater saturation: Heavy rains can cause the water table to rise, pushing water and gases up through sewer lines or cracks in your foundation.
• External factors: If you live in areas with older infrastructure, such as in parts of St. Louis or Nashville, aging pipes and outdated systems might not handle increased water volumes well.

 

Steps to Diagnose and Fix the Issue

  Here are practical steps you can take to diagnose and potentially repair the problem:

• Inspect your home's drain traps to ensure that water is always present. Add water if any seem dry.
• Check for visible leaks or blockages in your plumbing system, especially around basement drains and access points.
• Hire a professional plumber to inspect your vent pipes and sewer lines with specialized tools like cameras, ensuring there are no blockages, breaks, or misalignments.
• If you have a septic system, have a specialist assess if it is functioning correctly and is free of blockages.
• Consider environmental factors by ensuring that the grading around your home directs rainwater away from the foundation and sewer access points.

 

Preventive Measures

  To help prevent this issue from recurring in the future:

• Schedule regular maintenance for your plumbing system to catch and repair small issues before they turn severe.
• Keep the storm drains and gutters clear of debris, especially before heavy rainfalls, to ensure that water flows freely.
• Ensure that your home's venting is in good condition, checking for any blockages like bird nests or debris that might hinder the escape of gases.
• Consider checking with local municipal services if recurring issues are prevalent in your neighborhood, as sometimes citywide sewer maintenance or upgrades are necessary.

Following these recommendations can help identify the source of the sewage smell and guide necessary repairs to maintain a safe and odor-free home environment.