 The paper examined the potential benefits of using baffles in horizontal drain water heat recovery, DWHR units installed in the shower waste pipes of residential buildings. It found that the addition of baffles increased the efficiency of the DWHR unit by up to 40%, leading to greater cost savings and reduced carbon dioxide emissions. However, the optimal design of the baffles must take into account the specific hydraulics of each individual system. This article was authored by Sabina Cordano book and Mariusz Starzak.