A distribution box is a passive flow-splitting device installed downstream of the septic tank's outlet and upstream of the leach field laterals. It receives pre-treated, settled effluent and routes it into two or more perforated lateral pipes that discharge into the soil. A septic tank distribution box, or D-box, is a junction box that connects the outlet pipe from the septic tank to the multiple distribution pipes heading to different sections of the drain field. more Audio tracks for some languages were automatically generated. From there, the wastewater goes through more pipes to the distribution box.