The idea of sharing a septic system with your neighbor doesn't appeal to everyone. Yet, for builders, shared systems make a lot of economic sense. While the treatment system is larger than an individual system, economies of scale create a substantial savings. In Rhode Island, where we live, the high water table and small lots typically necessitate the use of "alternative" septic systems such as sand filters and biofilters, which treat the effluent before it is pumped to the leach field (see "Alternative Septic Systems," 1/97). The cost of equipping ten homes with individual advanced treatment systems runs between $100,000 and $120,000. But the ten-home shared system described in this article will
