The electrically conducting, incompressible and isothermal Newtonian fluid-flow in unsteady tank drainage is studied. The perturbation method is employed to obtain solution and results have been compared with those of obtained by adomian decomposition method result. The results of adomian decomposition method are same as those of perturbation method. The Newtonian fluid solution is worked out with substitution ε = 0. Explicit expressions on behalf of velocity field, flow rate, relationship however will the times vary with length, average velocity and time needed for complete drainage are acquired. Impacts of different developing parameters on velocity profile, vz, flow rate and depth of the tank, H(t), are exhibited graphically.