This article presents a new approach for the computation of the water surface angle in pipes arranged in parallel. Estimating this parameter in partially filled pipes is an important task in the solution of many practical problems in the different branches of the engineering profession such as flow measurement and design of drainage networks, where the flow is mostly of the free surface type. This characteristic is needed in the trial and error classical solution and huge number of times. The new method is elaborated to overcome the laborious trial and error method. Here, the computation of the water surface angle becomes easy, simple, and direct.