ADS 04710090 4" Perforated 9 Pipe Septic Stack at 10' - Septic Stack units allow for exceptional soil contact without the use of gravel. The Septic Stack units disperse effluent into the voids in and around the specially-banded ADS pipe. This pipe is engineered with holes and slots, allowing it to disperse the effluent as it passes over the corrugations in the pipe.