If you are planning to build a new home or add an addition in the Hattiesburg area, you will undoubtedly hear the term "Perc Test" (Percolation Test). It is the single most important hurdle in the construction process. Without a passing perc test, you cannot get a permit for a septic system, and without a septic system, you cannot build your home. Here is what every landowner in South Mississippi needs to know.
A perc test measures how quickly the soil on your property can absorb water. Since a septic system eventually discharges treated wastewater into the ground, the soil must be able to "percolate" that water at a specific rate. If the soil drains too fast (pure sand), the water isn’t treated properly before it hits the groundwater. If it drains too slow (heavy clay), the yard will flood and the system will back up.
In our region, we often deal with "Yazoo Clay" or other dense soil types. These clays can be very tricky for perc tests. Often, a property might "fail" in one spot but "pass" just twenty feet away. This is why it is vital to have an experienced professional perform the test. We know how to read the landscape and identify the areas most likely to have the right soil composition for a successful drainfield.
The test involves digging several holes (usually 2 to 3 feet deep) across the proposed drainfield area. These holes are filled with water to saturate the soil, and then we measure how much the water level drops over a specific period. The results are measured in "minutes per inch" (MPI). If your MPI is too high, you may be required to install an alternative system, such as an aerobic treatment unit (ATU) or a mound system, which can be significantly more expensive.
In Hattiesburg, the best time to do a perc test is during the "normal" season. If you do it in the middle of a drought, you might get a false pass. If you do it during a flood, you will almost certainly fail. We work closely with the Mississippi State Department of Health to ensure all tests are performed according to regulation and provided with accurate data for your permit application.
Don’t leave your septic permit to chance. We are the region’s experts in soil testing and system design.
SCHEDULE A PERC TEST: (601) 884-8016Most perc tests are completed in a single visit, but the timeline depends on how quickly the test holes drain. Sites with heavy clay can take longer to read accurately since the soil needs to fully saturate before an accurate percolation rate can be measured.
A failed perc test does not mean you cannot build. It usually means a conventional gravity-fed drainfield is not suitable, and you will need an alternative system such as an aerobic treatment unit (ATU) or a mound system, which handle slow-draining soil differently but come with a higher installation cost.
South Mississippi soil is inconsistent, especially where Yazoo clay pockets are present. A property can fail in one location and pass twenty feet away because soil composition changes across even a small lot. This is why an experienced tester evaluates multiple spots rather than relying on a single hole.
MPI measures how many minutes it takes the water level in a test hole to drop one inch. A lower MPI means faster-draining soil, and a higher MPI means slower drainage. Your county health department uses this number to determine what type of septic system design your property qualifies for.
Yes. Testing during a drought can produce a false pass, while testing right after heavy rain or during flooding can produce a false fail. Scheduling during normal seasonal moisture conditions gives the most accurate read on how your soil actually performs.
Perc tests should be performed by an experienced septic professional and results are submitted as part of your permit application. We work directly with the Mississippi State Department of Health to ensure testing follows regulation and the data supports your permit approval.
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