Septic tanks are chambers made of PVC, fiberglass, or other materials. These are used for primary treatment of domestic waste-water (sewage). Here the settling and anaerobic procedures reduce organics & solids. But septic tanks offer only moderate treatment. They show a type of on-site sewage facility. The systems are more practical in rural areas. They are watertight chambers to treat blackwater and greywater. The septic tanks are designed with various factors like amount of water, number of users, temperature and waste-water characteristics. These are important for houses or public buildings etc. Also, they should be cared and monitored timely. There is robust and simple technology with no requirement of electrical energy. A few key advantages are: low operating costs, long service life and low space requirement.