In this work the effect of copper content on the phase composition and mechanical properties of brass in the cast state has been studied. It has been established that with an increase in the copper content in brass from 57,0 to 63,9 wt. % the proportion of the α-phase in the structure of the alloy increases from 30 to 68%. In this case an increase in the relative elongation of the alloy is observed. The tensile strength first increases (up to a copper content of 61 wt.%) and then decreases. The results of the study made it possible to recommend the range of copper content in brass for the manufacture of ball valves 60…61%.