U.S. Code of Federal Regulations
Regulations most recently checked for updates: May 20, 2019
(a) The frequency of patrolling mains must be determined by the severity of the conditions which could cause failure or leakage, and the consequent hazards to public safety.
(b) Mains in places or on structures where anticipated physical movement or external loading could cause failure or leakage must be patrolled -
(1) In business districts, at intervals not exceeding 4
(2) Outside business districts, at intervals not exceeding 7