How to Dig a Septic Tank

Digging a proper hole is critical to septic tank installations.

Selecting the location and digging the hole for the septic tank is a vital step in the process of installing an efficient and trouble-free septic system. Mistakes made in the installation of the septic tank can result in system failure and not only costly repairs, but a very nasty situation to endure. It is critical to get the tank installed correctly, the first time.

Things You'll Need

• Backhoe
• Shovel
• Tape measure
• Level
• Small flags

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Instructions

1. Select the location for your septic tank. Determine where the drain line will be exiting the home. The septic tank needs to be directly in line with this point if at all possible. Have no turns, curves or angles in the line between the house and the tank to ensure a smooth flow. If the main drain line can exit the home from two locations, select the one which will allow the septic tank to be located closest to the field lines. This will make the installation of the remainder of the septic system far easier. In most areas of the country the septic tank must be located a minimum of 10 feet from the home.

2. Mark out the area for the septic tank. Take the measurements of the septic tank you have purchased and add 2 feet to the length and width. Mark out these dimensions using small flags. Before digging, double-check all measurements including the distance from the foundation of the home. Once all measurements have been confirmed, use the backhoe to dig the hole for the septic tank. The sides of the hole need to be straight up and down and free of any large rocks or roots. The depth of the hole should be no more than 24 inches deeper than the overall tank height.

3. Prepare the base of the hole for the tank installation. The bottom of the hole needs to be smooth and free of any rocks, roots or other debris. It should also be as perfectly level as possible. Use the shovel or backhoe to level the base of the hole. Think of the bottom of the hole as the foundation of your septic tank. If your foundation is bad, your system will not meet your expectations. Be certain the bottom of the hole is tightly packed and presents a solid base for the tank to rest on. While some settling may take place, you want to avoid using loose soil to level the base. It is better to remove slightly more dirt and keep the foundation solid.

4. The hole is now ready for the tank to be installed. This should be done by a professional who has the experience and equipment to do the job safely. A concrete septic tank can weight several thousand pounds and is not something you will want to manhandle. Remain clear of the hole while the tank is being installed. Once the tank is installed immediately fill it with water. This will prevent the tank from "floating" out of the ground should the area become saturated from a heavy rain.

References

• Idaho Department of Environmental Quality: Homeowners Guide to Septic Systems