The optimal design of a water distribution networks has been recognized as a complex problem due to the nonlinear relationship between flows in the pipe sections, the disconnected nature of the pipe diameter dimensions, and the relevant constraints on hydraulic requirements and pressure requirements that cannot be easily solved by traditional methods. To solve this problem, the hybrid algorithm development study between gray wolf (GWO) and Harris hawk (HHO) is conducted in order to achieve the best balance between the exploration stage and the mining stage. The superiority of the GWO-HHO algorithm is verified when it provides an optimal solution to two typical water distribution networks, Twoloop and Hanoi network, which is much better than those of previous algorithms. The comparison and evaluation result shows that the GWO-HHO hybrid algorithm is extremely effective to solve the design problems of water distribution networks with superior results compared to GWO as well as other previous algorithms in the two typical studies to be reviewed. This result can be applied in practice for large cities when the demand of replacing the existing old networks is more and more urgent and important.