The effi ciency of the irrigation system can be increased by reducing unproductive waterdischarges from channels. Hydrodynamic fl ow regulators control water supply on demandand are activated when water consumption in the downstream of the structure is reducedbelow the design value. Many works have been devoted to the theoretical and experimentalstudy of the hydraulic characteristics of the structures under consideration, but no universaldependence has yet been obtained for directly determining the amount of fl ow rates thatmerge in the regulator and the accuracy of water supply. The generally accepted schemefor merging fl ows in the regulator was the fl ow scheme in the exhaust tee, which later requiredmaking empirical corrections to align the theoretical dependencies with experimental data.In this paper, a fundamentally new approach to the calculation of hydrodynamic regulatorsis proposed – consideration of their operation as injection devices and the applicationof appropriate computational dependencies. The results of theoretical calculations arecompared with the existing data of experimental study of several versions of the fl ow partof the regulators. The output section of all structures was made in the form of a pyramidaldiffuser with a continuous fl ow. The fl ow coming from the upstream to the downstream wasinjecting, the fl ow circulating between the mixing chamber and the outlet section of the diffuserwas injectable. Comparison of experimental data and the obtained theoretical curve showeda good match. As a result of the research, it was found out that the accuracy of regulation canbe set by purposefully maintaining the necessary water horizon in the space above the diffuserand linking it with the amount of fl ow coming from the downstream through the spillway.