Y42x water pressure reducing valve and air pressure reducing valve are mainly composed of adjusting spring, diaphragm, piston, valve seat, valve disc and other parts. The diaphragm is used to directly sense the downstream pressure to drive the valve disc and control the opening of the valve disc to complete the function of pressure reduction and stabilization. Water pressure reducing valve and air pressure reducing valve can replace the conventional zoning water pipe and save equipment in the cold and hot water supply system of urban buildings and high-rise buildings. It can also play the role of reducing pressure and stabilizing pressure in the usual cold and hot water pipe network. The pressure regulating and stabilizing action of this product is stable. The water pressure reducing valve and air pressure reducing valve are applicable to the pipeline of water and non corrosive liquid medium.