In a system for leaching septic effluent from a source thereof, a first leach field has an input, a porous bed and means for distributing effluent from the input throughout the bed. A second leach field similarly has an inlet, a pervious bed and means for distributing effluent from that inlet throughout the pervious bed. Distribution means, having an intake coupled to the source, selectively feeds the effluent only to the input until the effluent level in the first field reaches a predetermined depth. Thereafter, the effluent is automatically fed to the inlet of the second leach field. The principle of operation is extended to the use of a third or more leach fields, the distribution means selectively feeding the effluent to the entrance to the third field only after the effluent in the second field reaches a preselected depth and so on.