This European Standard provides classification, general requirements and test methods for flexible, pre-insulated, directly buried district heating pipe systems. It is intended to be used in conjunction with parts 2, 3, 4, and 5. Depending on the pipe assembly (see Table 4), this European Standard is valid for maximum operating temperatures of 95 °C to 140 °C and operating pressures of 6 bar to 25 bar. The pipe systems are designed for a lifetime of 30 years. For pipe systems with plastic service pipes, the respective temperature profiles are defined in EN 15632-2 and EN 15632-3. NOTE For the transport of other liquids, for example potable water, additional requirements may be applicable.