The Septic Stack system from Advanced Drainage Systems is available in configurations of 9, 11 and 13 pipes. The units allow for exceptional soil contact without the use of gravel, functioning as a trickle filter to disperse effluent into the voids in and around specially banded ADS pipe, according to the maker. The pipe is engineered with holes and slots, allowing it to collect and disperse effluent as it passes over the corrugations in the pipe. Systems are available for use in both residential and commercial applications in trench, bed and mound configurations, as well as pressure dosing. 800-821-6710; www.ads-pipe.com.