The irrigation requires an efficient and effective method of water application to realize maximum return and conserve water resources. The low pressure sprinkler irrigation system is the most commonly used due to: its low energy cost, but the irrigation uniformity of this system is not constantly good because it is affecting by the design factors such as: nozzle type, nozzle diameter, operating pressure and spacing layout. But the most important factors are the operating pressure and nozzle diameter. In this study the effect of low pressure on the irrigation uniformity of the solid set sprinkler irrigation system was studied. Different low operating pressures (62, 82, 102 and122 kPa) were selected and different nozzle diameters (4, 5 and 7 mm) were used. The solid set layout was square (12 m between the sprinklers along the line and 12 m among the line). The catch-cans test was used to determine the uniformity coefficients such as: Christiansen's coefficient of uniformity (CU), coefficient of variation (CV), distribution uniformity of low quarter (DUlq) and distribution uniformity of low half (DUlh). The distribution characteristics such as: throw radius and rotation speed were monitored. A comparison was made between the results obtained from different combination of operating pressures and nozzle diameters. The results of this study showed that, CU, DUlq and DUlh were increased when the pressure increased for all the nozzles. The greater values of CU, DUlq and DUlh were found with the combination of 7 mm nozzle diameter and 122 kPa. The coefficient of variation was increased when the pressure decreased for all the nozzles. The throw radius and rotation speed were increased gradually when the pressure increased. The throw radius was not significantly affected by the nozzle diameter while the rotation speed was more affected by the nozzle diameter. © (2014) Trans Tech Publications, Switzerland.