The present study was designed to report experimental results for effective diffusion and longitudinal dispersion coefficients for both chlorine and fluoride added to water supply pipes. This is the first extensive study to find effective diffusion and dispersion coefficients for chlorine and fluoride added to water supply pipes. A pipe of field diameter and length was used to find dispersion coefficients for both chlorine and fluoride. The study covers the Reynolds number (R) from laminar and transitional flows (R = 200-20,000), for which more correct information about the dispersion coefficients might be needed in the literature. The paper first presents the solution of a two-dimensional (2D) advection-diffusion-reaction equation of concentration movement in a pipe. Second, it presents the analytical solution of a one-dimensional (1D) advection-dispersion-reaction equation. Third, by using the numerical and analytical solutions, effective diffusion and longitudinal dispersion coefficients of chlorine and fluoride are calculated. At the end, simulation of part of a real network with the results reported in this study is presented. (C) 2021 American Society of Civil Engineers.