I work for an engineering consulting company and now we are in the process of developing conceptual and basic engineering for a project involving the transportation and supply of raw water for two new units. Water Treatment and Potable systems will be installed inside both units in order to supply drinking water to service system. Transportation system includes a first section of 10 in dia - 22.2 km lenght, and a second section of 8 in. 28.2 km lenght, both in carbon steel pipe. First section Working pressures will vary from 230 psi to 130 psi, and the second one from 160 psi to 60 psi @ 35 Celsius degrees (including a pump station at the end of first section). Entering both units, pressure regulating valves will be installed in order to decrease the pressure. Our concern is based on if the transportation piping system should be designed per AWWA standards, or because of the high working pressures it requires to be designed per ANSI/ASME B31.4, B31.1 or B31.3?? What are the maximum working pressures in water steel pipelines, in order to be considered under the scope of AWWA standards??

Your application pressures appear well within the capabilities of AWWA steel pipe, or for that matter modern/standard cementlined ductile iron pipe per AWWA or ISO 2531 standards. Alhough standard minimum class AWWA ductile iron pipes in such sizes are listed for a maximum working pressure plus surge of 350+100 = 450 psi, both steel and ductile iron pipes in such sizes as you are talking about have been successfully used in the past at even greater pressures.