Updated Design Standard for Siphonic Roof Drainage Systems Is Now Available   We are pleased to announce that ASPE/ANSI 45-2025: Siphonic Roof Drainage was approved as an American National Standard by the American National Standards Institute (ANSI) on May 5, 2025. ASPE/ANSI 45-2025 applies to engineered siphonic roof drainage systems intended to prime and operate full bore