(a) No person may operate a segment of a high-pressure distribution system at a pressure that exceeds the lowest of the following pressures, as applicable:
(1) the design pressure of the weakest element in the segment, determined in accordance with this Part;
(2) 60 psig (414 kPa), for a segment of a distribution system otherwise designated to operate at over 60 PSIG (414 kPa), unless the service lines in the segment are equipped with service regulators or other pressure limiting devices in series that meet the requirements of section 255.197(c) of this Part.
(3) 25 psig (172 kPa) in segments of cast iron pipe in which there are unreinforced bell and spigot joints;
(4) the pressure limits to which a joint could be subjected without the possibility of its parting; or
(5) the pressure determined by the operator to be the maximum safe pressure after considering the history of the segment, particularly known corrosion and the actual operating pressures.
(b) No person may operate a segment of pipeline to which paragraph (a)(5) of this section applies, unless overpressure protective devices are installed on the segment in a manner that will prevent the maximum allowable operating pressure from being exceeded, in accordance with section 255.195 of this Part.