— the device of the septic tank is much cheaper than the treatment plant, but it will be more expensive in operation;
— the device of the septic tank is better when there are few drains in the house (people are unstable, or few people live). With a septic tank of 8 meters of cubic, it is designed for two weeks of drainage for a family of 4 people. Local cleaning is more effective when many people live in the house, in this case there is no need for additional costs for regular cleaning the septic tank;
