a pressure reducer for fluid lines , with a sealing piston as stop element , with an equalization piston as a means for pressure equalization , with a single - part or multi - part connecting means by which the sealing piston and the equalization piston are rigidly connected with one another , with a valve seat , in conjunction of which the sealing piston defines a flow - through opening , against which the sealing piston seals when the valve is closed and which the connecting means penetrates , and with guide means which are directly or indirectly rigidly coupled with the connecting means and guide an arrangement composed of at least the equalization piston , connecting means and sealing piston in each operating position , wherein the guide means are arranged in the region of the valve seat between the sealing piston and the equalization piston .