Pipelines with multiple outlets are used extensively for irrigation under various types of surface, sprinkler and trickle irrigation systems. In this research, a lateral pipeline with two diameters (tapered), laid on horizontal, uphill and downhill slopes that usually faced in design were investigated using back stepwise method. Effect of different parameters such as variation of friction factor along the pipeline, variation of discharge with head and velocity head on the total head loss and pressure along the pipeline was studied. Location of average operating pressure head along the pipeline for different slopes and tapering length ratios, which is important for computing the inlet and end pressures head, was estimated. Furthermore, empirical equations for estimating the ratio of head loss at location of average pressure head to the total head loss were developed. Then the pressure head at the upstream end or downstream end can be computed using friction correction factor method. The results showed that neglecting the effect of variation of friction factor underestimate the value of head loss along the lateral and neglecting the effect of variation in discharge overestimate the value of head loss, therefore, neglecting effects of the two parameters at the same time leads to a value of head loss very near to the value of exact solution. The velocity head have small effect on the head loss and can be neglected at sprinkler laterals but it has effect on the total head. Finally, example is given to show how to use the proposed empirical equations at inlet and end pressure computation.