WELD Septic tanks are tight tanks underground that collect the totality of domestic water a household produces, eliminate polluting materials in good measure concentrated material waste from water and ensure retention of solid materials and floating waste. In some cases, it can be an economical alternative for water sanitation networks from zones where there is not a centralized domestic wastewater treatment plant. It is obvious that the number of houses in the area should not be high because these systems, household wastewater treatment have limited capacities, in terms of volume.