Septic Tanks and Systems for Homes and Property
Septic Basics | How it Works | Potential Problems | What to Write into the Contract

Septic Basics

A septic tank also known as a septic system is a small scale sewage treatment system common in areas with no connection to main sewerage pipes. Septic systems are a type of On-Site Sewage Facility.

Sewage treatment, or domestic wastewater treatment, is the process of removing contaminants from wastewater, both runoff and domestic. It includes physical, chemical and biological processes to remove physical, chemical and biological contaminants. Its objective is to produce a wastestream (or treated effluent) and a solid waste or sludge also suitable for discharge or reuse back into the environment.

Typically, sewage treatment involves three stages, called primary, secondary and tertiary treatment. First, the solids are separated from the wastewater stream. Then dissolved biological matter is progressively converted into a solid mass by using indigenous, water-borne bacteria. Finally, the biological solids are neutralized, then disposed of or re-used, and the treated water may be disinfected chemically or physically (for example by lagooning and micro-filtration). The final effluent can be discharged into a stream, river, bay, lagoon or wetland, or it can be used for the irrigation of a golf course, greenway or park. If it is sufficiently clean, it can also be used for groundwater recharge.

How it Works

A septic tank generally consists of a tank of between 1,000 and 1,500 gallons which is connected to an inlet wastewater pipe at one end and to a septic drain field at the other. These pipe connections are generally made via a T pipe which allows liquid entry and egress without disturbing any crust on the surface. Today the design of the tank usually incorporates two chambers (each of which is equipped with a manhole cover) which are separated by means of a dividing wall which has openings located about midway between the floor and roof of the tank.

Wastewater enters the first chamber of the tank, allowing solids to settle and scum to float. The settled solids are anaerobically digested reducing the volume of solids. The liquid component flows through the dividing wall into the second chamber where further settlement takes place with the excess liquid then draining in a relatively clear condition from the outlet into the leach field, also referred to as a drain field, or seepage field, depending upon locality.

The remaining impurities decompose in the soil, and the water is eliminated by filtering fluids through porous materials into the soil, and eventually taken up through the root system of plants or added to the groundwater. A piping network, often constructed in a stone filled trench, distributes the wastewater throughout the field with multiple drainage holes in the network. The size of the leach field is proportional to the volume of wastewater and inversely proportional to the porosity of the drainage field. The entire septic system can operate by gravity alone, or where topographic considerations require, with inclusion of a lift pump.

How often the septic tank has to be emptied depends on the volume of the tank relative to the input of solids, the amount of indigestible solids and the ambient temperature (as anaerobic digestion occurs more efficiently at higher temperatures). In general it is rare for a septic tank system to require emptying more than once a year, and by careful management many users can reduce emptying to every 3 to 5 years. When emptying a tank, only a small residue of sludge should be left in the tank. Anaerobic decomposition is rapidly re-started when the tank re-fills.

A properly designed and normally operating septic system is odor free and besides periodic inspection and pumping of the septic tank should last for decades with no maintenance.

A well designed and maintained concrete, fiberglass or plastic tank should last about 50 years.

Potential Problems

• Excessive dumping of cooking oils and grease can fill up the upper portion of the septic tank and can cause the inlet drains to block. Oils and grease are often difficult to degrade and can cause odor problems and difficulties with the periodic emptying.
• Flushing non-biodegradable hygiene products such as sanitary towels, cotton buds etc. will rapidly fill or clog a septic tank and these materials should not be disposed of in this way.
• The use of waste macerators or grinders for disposal of waste food will cause a rapid overload of the system and early failure.
• Certain chemicals may damage the working of a septic tank, especially pesticides, herbicides, materials with high concentrations of bleach or caustic soda (lye) or any other inorganic materials such as paints, solvents etc.
• Roots from trees and shrubbery growing above the tank or the drain field may clog and or rupture them.
• Playgrounds and storage buildings may cause damage to a tank and the drainage field.
• In addition, covering the drainage field with an impervious surface, such as a driveway or parking area, will seriously affect its efficiency and possibly damage the tank and absorption system.
• Excessive water entering the system will overload it and cause it to fail. Checking for plumbing leaks and practicing water conservation will help the system's operation.
  
  If the system is damaged or malfunctions, contact your local health or environmental authority before attempting any repairs. Improper repair can result in costly mistakes and potential health hazards.

Info and photos courtesy of Wikipedia.org.


What to Write Into the Contract

When purchasing a home, it's a good idea to write a Septic Tank Pump Out into the contract or get information about when it was last done. This way, you know what you're starting with and the company providing the pump out can give you information regarding how full it was etc.

Make sure you familiarize yourself with the care of a septic system or you can have a huge problem on your hands.


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