A septic tank includes a chamber, an inlet through which waste water enters the chamber, an outlet, and an outlet pipe mounted to the outlet. At least one partitioning member is mounted in the chamber and separates the chamber into at least a first subchamber adjacent to the inlet and a second subchamber adjacent to the outlet. The partitioning member includes a plurality of through-holes allowing communication between the first subchamber and the second subchamber. The partitioning member prevents the suspensions and deposits in the first subchamber from entering the second subchamber. A submersible pump may be mounted in the first subchamber for creating recycling currents.