A deterministic model was developed to design the subunit drip irrigation system Different pipe diameters and lengths of lateral and telescopic manifold pipe with uniform slopes were studied. The model estimated lateral and emitter discharges and pressure head distribution along a lateral and manifold starting from the downstream as well as uniformity calculation. The friction head loss between successive emitters, laterals and manifold were estimated using the Darcy-Weisbach formula. The change of the velocity head, the changes of momentum along the lateral and manifold and the loss due to emitter connection were also considered. The model for designing manifold was run successfully for supplying water to one-side and two-side laterals. Field studies were undertaken to test the validity of the computer solutions. Emission flow and pressure distributions were measured and compared quite well with those predicted from the computer model. The model has been verified under different lateral lengths, diameters and slopes, different emitter types (exponents) and barb size diameters and their interactions. The results indicated that, the average deviation percentage for 140 emitter discharges along lateral No.1, 30 and 60 (first- middle- far), were 1.24, 1.65 and 8.3%, respectively. The average deviation percentage for discharge variation, pressure head variation and uniformity coefficient for 60 laterals along manifold were 1.8, 2.1 and 2.6%, respectively. Generally, uniformity coefficient (U_C) increased with increasing lateral length until certain length then U_C remarkably decreased. The trend of U_C with lateral length has neglected difference between flat and uphill lateral up to 5% slope. While U_C improved remarkable for downhill slope with different lateral diameters. U_C tends to decrease with increasing emitter exponent and U_C remarkably decreased from 0.96 to 84% with changing slope from 5% downhill to 5% uphill, respectively for laminar emitter. Decreasing rates of U_C with increasing emitter exponent were 3.5, 9.2 and 15.7% when slope changed from -5, zero and 5%, respectively. U_C decreased with increasing barb size diameters as increasing lateral length. U_C remarkably improved with increasing lateral diameters.