The article deals with the issues of ensuring the safe dosing of small volumes of chemical reagents with positive displacement pumps. The results of simulation of hydrodynamic processes in valve assemblies are presented. Studies have shown the low efficiency of the reagent supply process using ball and poppet valves. The use of hydraulic diaphragm and vortex diodes is proposed. Based on amathematical modeling, the design features of hydrodiodes and the parameters of their effective operation are substantiated, which makes it possible to exclude fluid pulsation and increase the flow rate. A diaphragm hydrodiode is suitable for a metering pump with a flow rate of at least 5 l/h. The vortex is capable of replacing ball and poppet valves at low and ultra-low flows, and it has been established that its diode resistance is more than 6, and its diode is more than 2 in terms of flow.