The advantages of septic tanks include the simplicity of their design, ease of installation, maintenance. For example, for a family where about five members, there would be enough septic tank with a volume of 2-3 m3. Septic tanks of this volume and use — clean only once a year. It is necessary to name a significant minus inherent in the idea of septic tanks — a low level of cleaning. Three -chamber septic tanks — and they are unable to give out a high degree of cleaning.