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BASICS OF SEWAGE OR ON-SITE SEPTIC SYSTEMS

First You Need To Know How Your System Works

Before you talk with a septic specialist, it's good to understand the basics of how your your sewage treatment system works.

Sewage is all the wastewater that comes from your house. Your toilet, dishwasher and washing machine, sink and shower drains all produce wastewater. And with that water come solids and grease. In fact, up to 50% of domestic sewage is created by your clothes washer and toilet. Your dishwasher produces 3%, and your bath, shower and sink faucets produce the remaining percentage.

As all this wastewater exits your house, it enters your septic system. When a septic system is designed, the designer and local government will determine the size and type of the septic system based on the number of bedrooms in the home. It’s assumed that each bedroom can accommodate two people. If your residence houses more people than the septic system was designed for, you can overload the system and it may fail.

The design of your septic system will be influenced by site characteristics such as existing structures, slopes, wells, streams and other environmentally sensitive areas.

The Importance of The Soil

Now, did you know that there are typically 40 million bacterial cells in a single gram of healthy soil? These soil microbes break down pathogens (harmful microbes). They are the key ingredient in treating wastewater from your septic system once it reaches the soil of your leach field. Pathogens from wastewater adhere to the soil particles of the leach field, and are broken down by microbes before it seeps into the groundwater.

soil microbe chart

The type and amount of soil on a property is one of the most important things to consider when designing a septic system. The soil test helps determine the type and depth of the soil on the property. (this used to be called the Perc Test.)

Generally, a soil test involves digging a hole roughly six feet deep and three feet wide with a backhoe. Soil layers and soil types are examined to determine absorption rates. It’s also important to measure the vertical separation, which is the depth of the soil on the property between the bottom of a drain field and the top of a restrictive layer. A restrictive layer might be bedrock, groundwater or an impermeable layer where water will no longer flow down through the soil and receive treatment.

In short, you can think of this area of soil as the filter for pathogen removal. The depth of this soil “filter” will help determine the system type that’s best for your property.

Different systems work best for different soils and different depth of soil. Learn more about system types here.