Private interceptor mains six inches or larger must have a manhole at the most upstream point and at intervals not more than what distance, and at every 45-degree change in direction?

• A. 400 feet and 45-degree changes
• B. 600 feet and 30-degree changes
• C. 300 feet and 60-degree changes
• D. 800 feet and 90-degree changes

Answer: (A)

Access for cleaning and inspection is the key idea. For private interceptor mains six inches or larger, a manhole must be located at the most upstream point and then at intervals not exceeding 400 feet, plus a manhole at every 45-degree change in direction. This spacing ensures you have a reachable point for rodding and cleaning wherever a blockage might occur, while preventing long, hard-to-clean runs between access points. The other distance and angle options would either extend the distance between access points beyond what’s practical or require too abrupt a bend for maintenance equipment, so the 400-foot interval with 45-degree changes is the standard.