An impact reducer for drainage stacks includes a first pipe section with a first internal passage having at least five alternating bends along its longitudinal axis, a bypass vent in a second pipe section having a second internal passage parallel to the longitudinal axis and a clean out plug in a third pipe section having a third internal passage at a radial angle with the longitudinal axis. First and second end fittings are located on the impact reducer for connecting the device to a drainage pipe. The impact reducer adjusts the turbulent flow of water falling in the drainage stack, converting the turbulent flow to laminar flow before the lower bend fitting of the drainage stack, which protects the lower bend fitting from impact shock.