(a) Each cast iron caulked bell and spigot joint that is subject to pressures of 25 psig (172 kPa) or more must be sealed with a material or device which:
(1) does not reduce the flexibility of the joint;
(2) permanently bonds, either chemically, mechanically or both, with the bell and spigot metal surfaces or adjacent pipe metal surfaces; and
(3) seals and bonds in a manner that meets the strength, environmental, and chemical compatibility requirements of sections 255.53(a)-(b) and 255.143 of this Part.
(b) Each cast iron caulked bell and spigot joint that is exposed for any reason, must be sealed by a means other than caulking.