- Building & Codes
- Private Wastewater Systems (Septic)
- What is a Septic System?
What is a Septic System?
Where city sewers are not an option, private wastewater systems, or septic systems, are responsible for handling household wastewater instead. Septic systems are designed to treat the wastewater and allow it to be absorbed by the soil and through evaporation without causing contamination, health nuisance, or odor.
There are two (2) main parts to every septic system; A septic tank and an absorption field.
A septic tank in crucial to the function and life of your septic system. It is the first stage of treatment for your wastewater when it leaves you house. The interior plumbing in your house should all feed directly into a septic tank outside of your home. The septic tank's job is to hold wastewater for an adequate amount of time to allow microorganisms to decompose of household waste and treat the wastewater before it leaves the tank. This is done by separating the waste into three distinct layers.
The scum layer on top is where the fats, oils, and greases reside along with anything less dense than water. On the bottom side of this layer is where the microorganisms live the treat and breakdown any wastewater in your septic tank.
The wastewater layer is a relatively clear layer composed of primarily liquid. This liquid is essential for the microorganisms to survive and function in your septic system. As the microorganisms breakdown any suspended solids in this layer they sink to the bottom and become part of the last layer, the sludge.
The sludge layer is all the solid waste and anything else that made its way to your septic tank that is more dense than water. This layer continues to grow with continued use of your septic system and the only way to remove it is to have your tank pumped by a licensed septic disposal contractor.
As you can see from the graphic above there are several part of your septic tank other than the tank itself that are crucial to ensure the continued use of your system without issue.
The first is the inlet and outlet tees. These tees extend from the pipes in and out of your tank to below the scum layer into the water. This causes hydraulic pressure to force wastewater up the tee and out the absorption field every time your flush or run water in your house. These tees ensure that the scum layer on top remains in the septic tank with the sludge layer so that no solids make their way to your absorption field. Without these solids can quickly clog and reduce the efficiency of your absorption field.
The other part of a septic tank is the riser and lid. All new septic tanks are required to have a riser and lid at grade for pumping, maintenance, and inspection. Also, whenever a property is sold in the City of De Soto a riser and lid is required to be installed on existing tanks that pass inspection. This riser and lid allows access to your tank for routine pumping without having to dig up your yard. These risers and lids, when installed correctly, are also much more water tight that the concrete lids that are on top of your septic tank underground which will ensure no ground water enters the tank overwhelming your system.
When the wastewater leaves your septic tank it enters what is known as an absorption, or lateral, field. This is the part of the system where the water is absorbed by the soil and grass above. At its most basic, an absorption field will consist of a series of pipes with holes in them in gravel trenches that allow the water to leak out of the pipes and into the soil totally underground. From there the wastewater is further treated by filtration into the soil and absorption by the grass above.
Absorption fields are not always as simple as pipes in gravel trenches though. The soil on your particular property dictates what type of absorption field will allow for the wastewater to be disposed of underground safely and effectively. Things such as rock and heavy clay can make this difficult for traditional systems and alternative systems must be used.
Often times in De Soto, rock or heavy clay is found when doing a soil analysis that requires the use of a system that differs from your traditional lateral field. Sometimes these systems will have to be pumped which requires a separate tank in addition to your standard septic tank. This tank will house a pump that will remove the wastewater from your tank into your absorption field. These tanks with pumps should also have audible and visual alarms installed to ensure notification if there is a failure before it becomes a major issue.
Often times these alternative type absorption fields are a sand and gravel based system designed to treat and filter the wastewater before it reaches an impermeable layer in the ground such as rock or clay. These systems are highly specialized in their function to ensure that the wastewater is treated properly before it is enters the soil or evaporates into the atmosphere.