Reuse of wastewater has been widespread in this era to support the water sustainability process. Therefore, treated wastewater should be conveyed to suitable places and adopted for different uses. This study presents an empirical relationship between the Darcy-Weisbach and Hazen-Williams equations for four types of pipe material (ductile iron, GRP, concrete, and plastic) by using WaterCAD Version 8i. Two hydraulic models were developed to estimate the head loss in pipes by using different diameters: first, using pipe diameters from 800 mm to 1,200 mm for a flow rate of 1.16 m3/s, second, adopting pipe diameter from 1,600 mm to 2,000 mm for a flow rate of 4.63 m3/s. The study results are the head loss values obtained from the Darcy-Weisbach and Hazen-Williams equations, which were used to correlate them using IBM SPSS Statistics. The correlation coefficient between both equations turned out to be 0.991, 0.990, 0.990, and 0.990 for ductile iron, GRP, concrete, and plastic pipe materials. Additionally, the relationship between head loss and pipe diameter is negatively proportioned for both equations. Also, both head loss equation results are the same. The head loss values in the Darcy’s equation were higher for ductile iron and GRP materials, while being lower for concrete and plastic materials for both models. Selecting concrete or plastic pipes to convey treated wastewater is better than other pipe materials. Another conclusion is that the pipe diameter affects the head loss magnitude irrespective of the kind of equation whether Darcy-Weisbach or Hazen-William equation. Finally, this relationship is very useful for designers in converting the head loss values obtained using these equations.

Introduction. To solve the problem of water shortage for irrigation in the city of Kerbala (Iraq), for the first time, a decision was made to use treated wastewater from urban wastewater treatment plants. Transportation of water from treatment facilities to irrigated lands is carried out through a pipeline in a pressure mode. The article compares the results of simulation modeling of WaterCAD V8i at various flow rates in a pressurized water supply system with the results of laboratory studies for three types of pipe materials (100 mm diameter steel pipe with polymer coating, 100 mm diameter polyethylene pipe and 100 mm diameter steel pipe with cement-sand coated (diameter 90 mm)). The purpose of the work is to verify the results obtained in the WaterCAD V8i program by conducting experiments for various types of pipes. Materials and methods. During the experiment, the characteristics of the flow were studied. Results. Comparison of the experimental results with the results obtained using the WaterCad V8i simulation model showed that the hydraulic parameters (pressure loss, friction coefficient) are close in values, but the WaterCad V8i program recorded higher values for pipes (steel pipe with a diameter of 100 mm with a polymer coating and a polyethylene pipe with a diameter of 100 mm). The high convergence of the results for a number of hydraulic parameters can be noted. Conclusions. The results of the work carried out by comparing the experimental data with the calculated ones obtained using the WaterCAD V8i program allow us to conclude that it can be widely used in practice to determine the hydraulic performance of pipelines.

Introduction. To solve the problem of water shortage for irrigation in the city of Kerbala (Iraq), for the first time, a decision was made to use treated wastewater from urban wastewater treatment plants. Transportation of water from treatment facilities to irrigated lands is carried out through a pipeline in a non-pressure mode. Using the Water Card simulation model, the optimal pipe diameters for two flows, 1200 and 2,200 mm, were selected. The capacity of the existing treatment plant is 1.16 m3/s or 100,000 m3/day, and after the introduction of new treatment facilities, the flow rate will increase to 4.63 m3/s or 400,000 m3/ day. The aim of the work was to experimentally confirm the choice of the optimal diameter of the pipes and determine the hydraulic characteristics of the flow in it. In this regard, in laboratory conditions, experimental studies of the hydraulic characteristics of the flow in a polyethylene pipe with a diameter of 100 mm in the range of slopes (0.005–0.03), with fluid flow in non-pressure, were carried out. Using the theory of hydrodynamic similarity, the results of experimental data were recalculated for pipe diameters of 1200 and 2,200 mm. As field data, when modeling hydrodynamic similarity, the results obtained in the simulation model are taken into account. In world practice, there is experience in the reuse of treated wastewater, but water is supplied to the place of consumption in most cases through open channels. For the first time, pipes of large diameters are used in this work, which requires a more detailed study of the hydraulic parameters of the flow in it. Materials and methods. Using the theory of hydrodynamic similarity, the results of experimentally obtained hydraulic parameters were calculated for plastic pipes with a diameter of 1200 mm at a water flow rate of 1.16 m3/s and 2,200 mm at a flow rate of 4.63 m3/s. Results. Conducting experimental studies and recalculating experimental data from a similar model to a full-scale object (the results obtained using the Water Card simulation model are used as a full-scale object) using the Froude method with similarity coefficients made it possible to obtain the following values of average flow rates, hydraulic friction coefficients λ, Chezy coefficients C, Reynolds numbers and other flow characteristics when filling the pipeline from 0.1 to 0.8 for pipes with diameters of 1200 and 2,200 mm. Conclusions. Conducting laboratory studies to determine the hydraulic characteristics of a polyethylene pipeline with a diameter of 100 mm as a model and substantiate the hydraulic similarity of the model and nature, in the form of plastic pipes with diameters of 1,200 and 2,200 mm, respectively, will allow designing a gravity system of main pipelines for transporting treated wastewater in the city of Karbala (Iraq). Further, the data of the simulation model are used as field data.