In this paper, a simple irrigation pipeline system is proposed to represent the common situation of lifting water from a reservoir to another higher reservoir through a pipeline. Bentley HAMMER model is used to perform simulation and analysis of steady state and transients in the irrigation pipeline system. To protect the irrigation pipeline system against positive and negative hydraulic transient pressures due to power failure, a hydro pneumatic tank is employed. The diameter, liquid and tank volumes are studied versus max pressure and vapor volume affecting the irrigation pipeline system. It is concluded that decreasing the diameter till 1/6 times the pipeline diameter, the max pressure decreases. More decreasing the diameter, the max pressure increases. Decreasing the diameter till 1/4 times the pipeline diameter, no vapor is formed. More decreasing the diameter, the vapor exists. As the liquid volume decreases; the max pressure increase for each value of the diameter, while the vapor increases for the diameters less than or equal 1/6 times the pipeline diameter. The time after which check valve of pump closes varies according to the diameter and liquid volume. Design chart and nine design equations are obtained to get an easy and effective design for hydro pneumatic tank. Employing the deduced design chart or the obtained design equations accomplish savings 55% in the diameter and 51% in liquid and tank volumes for the hydro pneumatic tank.