Why Does My Septic Tank Smell?

By Elizabeth Michael

September 10, 2024

Walking out your front door to be greeted by a strong, pungent odor can only mean one of two things: Either somebody dumped a carton of eggs all over your lawn, or there's something amiss with your septic tank.

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Septic tank odors can occur for many reasons, from ventilation problems to serious blockages that require professional intervention. In certain situations, a cup of baking soda may be enough to rid your tank of the stench, while other odors may indicate plumbing emergencies.

Reasons Your Septic Tank Stinks

Because septic tanks handle water waste, a common belief is that odors should be expected. However, if your tank is functioning correctly, any odors created by the waste should be released through the vent pipes without stinking up your indoor or outdoor space. If you notice a strong odor emitting from your tank or coming into your home through a floor drain or sink drain, it should be addressed as soon as possible.

Clogged or Blocked Drain Pipes Inside the Home

If a drain inside your home becomes blocked or clogged, it can't efficiently carry water waste into the septic tank. This can lead to toxic sewage gases backing up into the home, causing a telltale "sewer gas" odor. If you're concerned about a possible clogged or blocked drain pipe, it's important to schedule a plumbing service immediately. Plumbers have specialized tools and equipment to safely locate and eliminate all types of blockages and get your plumbing flowing in the right direction.

Loose or Damaged Tank Cover

If the cover that sits over your septic tank's access point is loose, cracked or damaged, it can allow septic odors to escape. Because septic tank covers can be quite heavy and the gases leaking out may contain toxic chemicals, it's always best to leave this job to the professionals. An experienced plumber can replace your tank cover safely and efficiently, and they'll also inspect your septic system for any additional issues.

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High pH Levels

If the pH levels in your septic tank are too high, this can affect the natural bacteria and microbes that break down solid waste. If a high pH level is to blame, you'll most likely catch a whiff of rotten egg odors in and around your tank. Fortunately, this can usually be fixed by adding baking soda to the mix. Flush a cup of baking soda down your toilet, or pour a cup down an indoor sink drain. Repeat the process on a weekly basis to balance out the pH levels in your tank and eliminate the odors. Ideally, pH levels should range between 6.8 and 7.6, and many retailers sell portable pH meters for convenient home testing. If the odors and/or pH levels don't improve, contact a plumber to inspect your septic tank.

Ventilation Issues

Strong sewage odors inside the home can be due to a failing or blocked ventilation pipe. When sewage gas can't be released through the ventilation system, toxic gas can build up and make its way indoors. Sewage gas can be highly toxic, so you'll definitely want to contact a plumbing professional for assistance. They can replace the damaged pipe if necessary and install carbon filters over the working vent to help prevent future odors.

Full Septic Tank

If your septic tank is too full or on the verge of overflow, the pump that's responsible for pushing the wastewater into the drainage field may fail. When this happens, you may smell a strong sewage odor outside the tank and inside your home. Overflowing tanks can also cause sewage to back up inside the home via the floor drain.

This type of issue should always be handled by a professional plumber, as overflowing tanks must be pumped to restore normal water flow. Plus, handling raw sewage may increase the risk of illness. If it's been a while since your tank was pumped or you suspect it may overflow soon, contact a professional plumber immediately.

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