Water Flowing Underground: 25 Centuries of Waste Disposal BACKFILL Water Flowing Underground: 25 Centuries of Waste Disposal by Jon Vara Although there are over 25 million septic systems in the United States, with 400,000 more new ones being built each year, most homeowners — and more than a few builders — know almost nothing about how they actually work. Into this information void come authors Lloyd Kahn, Blair Allen, and Julie Jones, whose The Septic System Owner's Manual (2000; Shelter Publications, P.O. Box 279, Bolinas, CA 94924; 800/307-0131; www.shelterpub.com) tells you everything you might want to know about the subject, and at least a few things you might prefer not to know. The illustrations