Abstract: A sewage septic tank is described having a diversion system for diverting effluent from the tank from one drain field to another. A "Y" is provided on the outlet pipe of the tank to enable the effluent from such tank to be directed to either one of two drain fields. A gate valve is provided at the end of each arm of the Y to allow flow within the drain field associated therewith to be controlled. Thus, the effluent from the septic tank can be periodically diverted from one drain field to another so that such fields are allowed to alternately dry out. The position of the actuator for each of the valves provides a simple visual indication of the state of the valve at any given time.