Why does my basement smell after it rains?
Heavy rain overloads the sanitary sewer, pushing gas back up through floor drains with dry traps. Refill the traps with water and install trap primers on any drain that doesn't see weekly water.
Why it happens
The odor is often sewer gas, primarily hydrogen sulfide, pushed into the building when heavy rain pressurizes the municipal sewer system. While dry floor drain traps are a frequent entry point, the smell can also escape from improperly sealed sewage ejector pits. This gas, known for its distinct rotten-egg smell, is produced by bacterial activity in wastewater and is corrosive to building materials like concrete and copper pipes.
What to check
First, pour water into all basement floor drains to ensure their traps are full, creating a barrier against sewer gas. Next, inspect any sewage ejector pits. Check that the pit lid has a tight seal and is bolted down correctly. Also look for evidence of dried-out pump seals or check valves, as these can provide a path for gas to escape. Note if the pump runs in very frequent, short bursts, which can leave a sludge layer behind.
When to call a professional
If refilling drain traps does not resolve the odor, or if the smell is persistent, treat the situation as urgent and contact a professional. Sewer gas can contain toxic and explosive components, including hydrogen sulfide and methane, making further investigation by building staff dangerous. Professional service is required for tasks like cleaning ejector pits, which are considered confined spaces and demand specialized safety procedures.
How Luften handles it
Luften addresses sewer gas odors at the source. Our programs focus on treating sewage ejector pits by first cleaning the accumulated sludge and biofilm that produce hydrogen sulfide. After the initial cleaning, we install equipment for continuous metered dosing of treatment chemistry to prevent recurrence. This approach eliminates the problem, rather than just masking the odor. A specialist can conduct a free on-site survey to identify all odor sources and provide a written treatment plan.
Ejector Pit Treatment Program