Valves with high regulating capacity can significantly reduce the loss of tap water. The hydraulic characteristics of liquid discharge through orifice in the form of a "curved drop" made in thin walls of tap valve closure member are determined by theoretical and experimental studies. The relationship of the change in water flow rate for tap valves with orifice in the form of a “curved drop” to varying pressure is established. The comparison of flow characteristics for tap valves with closure members having a different shape of through hole is made. The obtained hydraulic coefficients allow to design the valves with a high regulating capacity. The results of the study are of interest for theoretical and practical tasks of designing and manufacturing valves for water supply. The use of closure members with a hole in the shape of a “curved drop” allows to reduce the loss of tap water of drinking quality. The study is ongoing. © 2018 Journal of Urban and Environmental Engineering (JUEE). All rights reserved.