Conventional In-Ground Septic Systems

A conventional system consists of a septic tank and subsurface soil absorption trenches. After the initial treatment in the septic tank, the effluent (partially clarified water from septic tank) travels to the conventional component. The effluent travels to the conventional component by gravity or pump. If the conventional is higher than the tank, a pump must be used to get the effluent up to the conventional.

The conventional component consists of a series of trenches. The quantity and size of the trenches depends on the loading rate of the soil in which it will reside and how many bedrooms are in the house.

Every bedroom is worth 150 gallons/day. If it is a business, than the designer of the septic system must refer to the Wisconsin Code to determine how many gallons/day the business will produce. The installer obtains the loading rate from the soil test. The total gallons/day the house/business produces is divided by the loading rate of the soil.

This number is how many square feet the conventional component must equal. For example, let’s use a 3-bedroom house that needs a conventional using stone and pipe. The formula using leaching chambers or EZ-flows is different.

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The soil test has a loading rate of 0.5.

450/0.5 = 900 square feet

The square footage of all the trenches must equal 900 square feet. Most commonly, the trenches are 6 feet wide. In this case, the conventional component could have 2 trenches 6 feet wide and 75 feet long or 3 trenches 6 feet wide and 50 feet long.

There are three ways the conventional component distributes effluent into the soil. The three ways are through stone & pipe, leaching chambers, or EZ-flows. Please click on the appropriate link to learn about more.

The final treatment of the effluent occurs in the soil. Each trench or cell receives an equal amount of effluent. The soil at the beginning of each trench receives the effluent generated by the house/business. Once the soil is saturated or clogged the effluent moves further down the trench. The soil beneath the conventional component removes pathogens, organic matter, reduction of contaminants by aerobic microorganisms and ion bonding to negatively charged clay particles. The soil serves as a fixed porous medium on which beneficial aerobic microorganisms grow. These organisms feed on organic matter present in the wastewater and help eliminate pathogens. Unless pre-treatment is used, a minimum of 48 inches of suitable soil is required for a conventional.

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