There are four main components in an average septic system. These are the pipe running from the house, the septic tank, a drainfield and the soil. The soil is very important to the operation of your septic system because microbes found in the soil help digest or remove most contaminants from the wastewater before it reaches the groundwater.
The pipe running from your house to the septic tank carries all waste water and waste products to the septic tank.
Septic tanks are buried and watertight and are usually made of concrete, fiberglass or polyethylene. The purpose of the septic tank is to hold the waste water until the solids settle creating a sludge and the oils and grease float to the surface creating a scum film. The tank will allow for partial decomposition of the solid waste while compartments and a t-shaped outlet prevent the sludge and scum from exiting the tank and entering the drainfield. Screens can also be used to prevent this from happening.
There are two basic types of septic systems. The system that most people associate with are the older style with the "lateral lines". In this type of system, the affluent is broken down by "anaerobically", or without oxygen. There is usually no mechanical device attached to these system whatsoever unless a lift pump is needed. Over time, the affluent breaks down and migrates into the lateral lines where it leaches out into the soil. You can often see these lateral lines in the dry summertime as bright green streaks.
The second type of system is the newest technology. These are called "aerobic" systems. These are actually mini-wastewater treatment plants not unlike the huge plants that might serve a city. The technology is really very simple. In this system, the matter is broken down in two different tanks. The first tank is the settling tank just like the tank on the older style systems. The material is broken down without oxygen and then moves from the first tank to the second tank. The second tank is has a pvc line run into the bottom which is attached to an air compressor at the surface. The air compressor is constantly forcing oxygen into the tank, thus breaking down the matter "aerobically" or "with oxygen". There is also a third tank, which is simply a holding tank. When the third tank reaches a certain height, a sprinkler pump within the tank pumps the water out to the sprinkler lines. Between the second and third tank is a pipe which can be easily accessed from the surface. About once a month, chlorine tablets are dropped into this pipe. The treated water slowly washes by the chlorine tablets and is chemically sanitized.
Below are the differant types of Septic Systems.
Conventional Gravity Flow Drainfield
This is a septic system where the effluent from the septic tank gravity flows into the drainfield (absorptive bed or leach field). This type of system requires a minimum of 48 inches of suitable soil before encountering a restrictive rock horizon or groundwater. The natural slope of the property cannot exceed 30%. There is no maintenance contract required.
Pumped Effluent Drainfield
This is a septic system where the effluent from the septic tank is pumped into the drainfield (absorptive bed or leach field) because the drainfield is located at a higher elevation than the septic tank. This type of system requires a minimum of 48 inches of suitable soil before encountering a restrictive rock horizon or groundwater. The natural slope of the property cannot exceed 30%. The negative to this type of system is that the pump may need to be replaced over time. There is no maintenance contract required.
Low Pressure Dose Drainfield
This is a septic system where the effluent from the septic tank is pumped into the drainfield (absorptive bed or leach field) providing equal distribution of the effluent simultaneously throughout the drainfield. This type of system requires a minimum of 24 inches of suitable soil before encountering a restrictive rock horizon and a minimum of 36 inches of suitable soil before encountering groundwater. The natural slope of the property cannot exceed 30%. The negative to this type of system is that the pump may need to be replaced over time. There is no maintenance contract required.
Soil Substitution Drainfield
This is a septic system where the drainfield may be constructed in soils which contain greater than 30% gravel, fractured rock, fissured rock, or other areas of high permeability where septic tank effluent could rapidly reach groundwater without undergoing adequate treatment through soil contact. A soil substitution drainfield is constructed similar to a conventional gravity flow drainfield except that a 2-foot thick soil buffer shall be placed below and all sides of the drainfield excavation. The natural slope of the property cannot exceed 30%. The negative to this type of system is that the substituted soil increases the price of the septic system. There is no maintenance contract required.
Mound Drainfield
This is a septic system where the drainfield is constructed above the native soil surface. A mound drainfield may only be constructed on sites with a minimum of one foot of native soil. However, approval for sites with less than one foot of native soil can be granted by the permitting authority on a case-by-case basis. This type of system requires a minimum of 12 inches of suitable soil before encountering a restrictive rock horizon and a minimum of 24 inches of suitable soil before encountering groundwater. The natural slope of the property cannot exceed 10%. The negative to this type of system is that the pump may need to be replaced over time and that the mound can be an "eye-sore" if constructed too high. There is no maintenance contract required.
Aerobic Treatment Unit with Surface Application
This is a septic system where the effluent from the septic tank is treated and sprayed on the ground like a sprinkler system. Land acceptable for surface application shall have a flat terrain and shall be covered with grasses, evergreen shrubs, bushes, trees, or landscaped beds containing mixed vegetation. There shall be nothing in the surface area within 10 feet of the sprinkler which would interfere with the uniform application of the effluent. The natural slope of the property cannot exceed 15%. The negative to this type of system is that the pump, aerator, and chlorinator may need to be replaced over time. A maintenance contract is required throughout the life of this septic system and some counties require that the system utilize a telephone line to notify the maintenance provider of time of malfunction or failure.
Aerobic Treatment Unit with Drip Irrigation
This is a septic system that may be installed in all classes of soil. The system must be equipped with a filtering device capable of filtering particles larger than 100 microns and that meets the manufacturer's requirements. The drainfield shall consist of a matrix of small-diameter pressurized lines, buried at least 6 inches deep, and pressure reducing emitters spaced at a minimum of 30-inch intervals. The pressure reducing emitter shall restrict the flow of effluent to a flow rate low enough to ensure equal distribution of effluent throughout the drainfield. This type of system requires a minimum of 6 inches of suitable soil before encountering a restrictive rock horizon and a minimum of 12 inches of suitable soil before encountering groundwater with the use of a chlorinator. The natural slope of the property cannot exceed 30%. The negative to this type of system is that the pump, aerator, and chlorinator may need to be replaced over time. A maintenance contract is required throughout the life of this septic system and some counties require that the system utilize a telephone line to notify the maintenance provider of time of malfunction or failure.
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