How Does Rain Affect My Septic Tank?

February 9, 2023 Published by Leave your thoughts

As you can imagine, heavy rain can have a significant impact on your septic system. This is especially true if your system has not been properly maintained or if it’s due for pumping. This is why it’s important to understand how rain affects your septic system and what you can do to prevent problems. 

Drain Field 

Rain affects the drain field, which is a critical part of your septic system. It is a network of pipes, trenches, gravel, and soil that helps to filter and dispose of your septic tank’s liquid waste. Water flows from your septic tank to the drain field through perforated pipes. The wastewater is then dispersed through the pipes and passes into the gravel layer, which is where it is filtered by organisms in the soil. During excessive rainfall, your drain field might not be able to absorb all of the wastewater and it could flood. This would not only be a nuisance, but it might also cause untreated waste to leak into the ground. 


In a typical system, wastewater enters the tank and is treated by enzymes before it is released into the drain field. The partially treated water passes through gravel in the drain field, where aerobic bacteria remove pathogens. Septic tanks are usually buried underground and the soil in the drain field absorbs excess runoff from your home. However, heavy rain can inhibit this process and prevent the soil from absorbing water properly. To avoid this problem, reduce the amount of water you use in your house and try to reroute roof drainage that goes into your drain field.  


Your septic system works through several components: an inlet pipe, a septic tank, and a drain field. Each of these systems is designed to deal with the volume of wastewater that flows through it. During normal, non-rainy conditions, untreated sewage (the liquids) flows from the inlet pipe into the drain field, where microbes break it down and purify it. But heavy rainfall floods the ground around the drain field, preventing the effluent from flowing out and causing the soil to become saturated. The water then backs up into the septic tank and floods back into the home. 

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