Section 192.747 - Valve maintenance: Distribution systems(a) Each valve, the use of which may be necessary for the safe operation of a distribution system, must be checked and serviced at intervals not exceeding 15 months, but at least once each calendar year.(b) Each operator must take prompt remedial action to correct any valve found inoperable, unless the operator designates an alternative valve.Amdt. 192-43, 47 FR 46851, Oct. 21, 1982, as amended by Amdt. 192-93, 68 FR 53901 , Sept. 15, 2003