D.C. Mun. Regs. tit. 25-D, § 710
Design, Construction, and Installation - Backflow Prevention, Air Gap*
Effective Oct 9, 200956 DCR 7975Authority: Section 4902 of the Department of Health Functions Clarification Act of 2001 (“Act”) (effective October 3, 2001), D.C. Law 14-28, D.C. Official Code § 7-731(a)(12) (2008 Repl.), and the Mayor’s Order 2006-10 dated January 27, 2006 Source: Final Rulemaking published at 56 DCR 7975 (October 9, 2009)District of Columbia, Office of the Secretary
710 DESIGN, CONSTRUCTION, AND INSTALLATION —
BACKFLOW PREVENTION, AIR GAP*
710.1 An air gap between the water supply inlet and the flood level rim of the plumbing fixture or equipment shall be at least twice the diameter of the water supply inlet and may not be less than twenty-five millimeters (25 mm) or one inch (1 in).
Source: Final Rulemaking published at 56 DCR 7975 (October 9, 2009).