The hydraulic resistance to a flow propagating in polyethylene pipelines with a velocity characteristic of flows propagating in gas-supply systems has been experimentally investigated. The experimental data have been processes statistically with the use of the maximum-likehood method and regression analysis. The hydraulicresistance coefficient has been approximated using the Colebrook-White, Prandtl, and other models. Corrections to the hydraulic formulas used for calculating polyethylene pipelines in the process of their designing and service are proposed.The study of the hydraulics of liquids and gases flowing in industrial pipelines is of great practical importance. The data fundamental for this field of research were obtained more than fifty years ago [1,2]. There are also many reference books [3,4] and textbooks containing information on this subject. However, the investigations carried out in the indicated field cannot be considered as completed. New publications devoted to various aspects of the pipeline hydraulics continue to appear [5][6][7][8][9]. The interest shown in this problem is explained by the following facts. The classical Nikuradse experiments [1, 2] were carried out with laminar, turbulent, and transient liquid flows propagating with different velocities. The data obtained for liquids were then extended to gases and supported by the experimental data on flows in industrial pipelines to a certain extent allowed by the apparatus used for measuring the parameters of the flows. More recent special investigations introduced certain corrections to the data obtained for flows at large Reynolds numbers [5] and for transient flows [6]. This has been possible due to the appearance of modern methods of measuring the parameters of flows with the use of computers.In the above-indicated works, gas flows in pipelines with artificial [1, 2, 7, 8] and natural [1, 2, 7-9] roughness were investigated. We also know of works containing data on regimes of flow in industrial gas pipelines [9, 10]; however, these data were obtained for steel pipelines.At present, polyethylene pipes are finding wider and wider application in gas-supply distribution systems. Polyethylene pipes have a number of advantages over the steel pipes: long service life (as long as 50 years), relatively low cost, high adaptability (suitability for inter-settlement, inner-town, and street service lines), and low inner-surface roughness that practically does not change with time. They are not prone to corrosion and, therefore, do not call for electrolytic protection. Polyethylene pipes will gradually supplant steel pipes in pipeline systems operating at a relatively low pressure. The foregoing points to the importance of development of models for simulation of flows in polyethylene pipelines.To date, one and the same formulas have been used in technological calculations of steel and polyethylene pipelines. These formulas differed only in the numerical values of the roughness coefficient. Such extrapolation of hydraulic models of flows was done wi...