Troubleshooting Your Septic System

2 Methods To Test Your Soil Before Installing A Septic System

Before you can install a septic system in your home's yard, it is necessary to test the soil to make sure it can accommodate the septic system's drainage field. The drainage field is important to ensure your septic system stays healthy and efficiently drains excess water from its tank into the surrounding soil. For this reason, the soil needs to have the proper mixture of sand and clay. Here are two methods you can use to test your soil's characteristics before installing a septic system drainage field in your yard.

Soil Bore Test

During a soil bore test, your yard's soil content is tested and also visually inspected to make sure it is sufficient to support a septic tank drainage field. This test will help you discover any layers of soil in your yard that can block the drainage of your septic system water. A block in your system's drainage can cause the water in your system to back up and turn your backyard into a septic system marsh. 

To complete a soil bore test, a soil test technician will excavate a series of deep holes in the ground throughout your yard. Then, they will visually inspect your soil and may also need to complete some laboratory testing on a sample of the soil. Sometimes it can be necessary to excavate a hole ten feet deep or more below the level of where you want to install your septic leach field to inspect the soil. Illinois, for example, requires three or four excavated pits to be dug at varying locations, at least 50 feet apart and at a depth of at least 60 inches. 

Excavating the soil at various locations will help you discover the different types and layers of soil from one area to another in your yard. A soil bore test may discover, for example, that you have sandy, well-draining soil in one part of your yard, and a layer of hard clay-like soil in another. It is also important to check the level of your yard's water table, as this can interfere with and block your septic drainage. 

This information from the soil bore test will tell you where it is best to install your septic drainage field. Check with your area's health department for the soil bore test requirements, as they can vary by your area. You can hire a local testing professional to complete the testing in your area according to your area's requirements.

Percolation Test

Many states also require a percolation soil test to make sure the soil in your yard can support a septic system. Conducting a percolation test will test how quickly water seeps into the soil of your yard. Make sure you check with your local health department to find out how many percolation test holes you need to complete. For a large septic drain field, you may need to test different areas of soil.  Also ask your local health department who can conduct the test, the time of year the test needs to be completed, and what rate of percolation your soil needs to have to be adequate for a septic system. Different states and counties can have different testing requirements.

For the percolation test, each hole will need to be dug at a depth of two feet. Make sure to check the depth with a tape measure. Fill each hole with water and allow the water to completely soak into the surrounding soil. This creates a simulated situation of an actual leach field site saturated with septic water. 

As soon as the water has soaked into the surrounding soil, fill the hole with water a second time. After 30 minutes, measure how much the water level has dropped with a measuring stick. Calculate the drop rate by taking 30 minutes and dividing it by the number of inches the water dropped during the test. For example, if your water level dropped only seven inches during the 30 minute test, 30 divided by 7 equals 4.28, which is a percolation rate of 4.28 minutes per inch and does not pass the test.

Depending on the state and county you live in, a general drainage rate can be between 15 to 105 minutes for each inch of water drop. If your soil drainage rate is outside of this range, your soil does not pass the test and is unsuitable for a septic leach field.

Use this information to test your soil before installing a septic system and leach field. For help installing your new septic system, contact a company like Martin Septic Service Inc.


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