Septic Tanks

Septic tank system is an important method for treating disposal of household wastes. It is mainly installed in the area which has no connection to main sewerage pipes. The Anaerobic environment of the tank helps the bacteria to decompose the wastes.

How It works?
The septic tank system work by separates wastewater to separate into layers. The bacteria present in the tanks decomposes the solid wastes that have settled to the bottom of the tank thereby transforming most of the wastes in solids and gases. The outflow pipe in the tank drain out the access liquid in the drainage system. The outflow, through a series of subsurface pipes is distributed throughout the drain field. Here effluent undergo final treatment as the soil absorbs and filters the liquid whereas rest of the materials is broke down by the microbes.

For different type of conditions, different types of septic tanks are used like:

• Conventional systems that use gravity to distribute the effluent
• Low pressure distribution system
• Mound systems

Grease and light particles that comes out with wastewater forms a layer of scum on top of the wastewater. They are prevented from escaping by the use of Baffles which are installed at the inlet and outlet of the tank.


It is not possible for the septic tanks to dispose all the materials which enters the system. The solid that is left behind and which is not decomposed need to be removed on a regular basis otherwise the system will fail.

It should be kept in mind that, the holding tank should be pumped out frequently because the solids can enter the pipes leading to and from the tank that can cause sewage to back up into the house or cause the drainage system to fail. These problems are not only costly but can pose a danger to public health. They can also cause pollution to both ground and the surface water through seepage.

Wastewater contains several undesirable pollutants. Pathogens such as viruses or bacteria can enter drinking water supplies creating a potential health hazard. Nutrients and organic matter entering waterways can lead to tremendous growth in the quantity of aquatic microorganisms. Metabolic activity of these microbes can reduce oxygen levels in the water causing aquatic life to suffocate.

Wastewater is distributed from the septic tanks to the distribution box through solid pipes. Here the wastewater is channelized into one or more perforated pipes set in trenches of gravel. It is here where water seep into the underlying soil. The wastes and the bacteria that are dissolved are trapped or adsorbed to soil particles or decomposed by microorganisms. The wastewater which is purified either moves to the ground water or evaporates from the soil. Trench systems are the most popular type of septic tank system that are used in new home construction.

Instead of drainfield some people prefer to install Seepage Pit (Dry Well). Dry Well has sidewall holes surrounded by gravel. The holes allow the liquid to seep. If in a area the condition is not fit to install conventional septic tank system then Sand Mound System is a good alternative.