This APP is a tool for finding the right size of pipes for wastewater and rainwater systems - and to assess whether the pipe is self-cleaning. The calculations are based on Mannings formula - full- or partially filled Pipes.The results are comparable to calculated values from model tools such as EPA-SWMM and DHI-MIKE URBAN. Defalt Manning number 76.However - input values and the results must be subjected to engineering assessment. The publisher can not take responsibility for the use of the APP.