Exposed layers of soils/ © Adobe Stock
When determining what type of onsite wastewater treatment system (septic system) to install, understanding the type of soil and its properties is paramount in making sure the right type of system is chosen. There are two ways to determine this:
Percolation Test: A percolation test, or perc test, is used to determine the rate at which water can infiltrate into the soil. It involves digging a hole, filling it with water, and measuring how quickly the water drains into the soil, helping assess the soil's suitability for different types of systems.
Soil Classification: A soil classification is the process of categorizing soil based on its physical and chemical properties. It involves analyzing factors such as texture, structure, moisture content, and organic matter. Soil classification helps determine the type of soil present and its characteristics, which can impact various applications, including septic system design.
A percolation test focuses on the water infiltration rate, while a soil classification provides a broader understanding of the soil’s properties. Both tests are important in assessing the suitability of soil for different purposes, including septic system installation. In some states, like Illinois, a percolation test is not accepted, and a soil classification is required. Many percolation tests were done by homeowners and are very inaccurate. A soil classification is performed by a licensed soil classifier, who must have an extensive knowledge of soil, ensuring an accurate report.
Contact your local health agency that oversees onsite wastewater treatment system installation or a professional sewage contractor to find out which test your local rules and regulations allow.
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Sign up for the free 10-week email course from PrivateWellClass.org. The class is a project of the University of Illinois and RCAP, with funding from USEPA.
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