Water control valve is a valve that is powered by pipeline medium pressure to open, close, and regulate. It consists of a main valve and attached conduits, needle valves, ball valves, pressure gauges, etc. Depending on the purpose of use and functional location, it can be evolved into remote control float valves, pressure reducing valves, slow closing check valves, flow controllers, pressure relief valves, hydraulic electric control valves, emergency shut-off valves, etc. The pilot valve operates in response to changes in the liquid level and pressure of the medium. Due to the variety of pilot valves, they can be used individually or in combination to enable the main valve to achieve individual and composite regulation of water level, water pressure, and flow rate. But the main valve body is similar to a globe valve. When the valve is fully open, its pressure loss is much greater than other valves, and the loss coefficients of each opening degree increase dramatically as they approach the fully closed state. The larger the valve diameter, the more significant it is.

Valves with the above characteristics are prone to water hammer impact when accelerating near the valve disc. When approaching full closure, the slower the valve action, the better. Therefore, throttling devices can be installed on the valve disc. In addition, the throttle and action parts of the pilot valve should avoid setting ultra small diameter holes as much as possible to prevent blockage. Filter screens should be added when necessary, and regular maintenance and installation of bypass pipelines should be carried out. Hydraulic control valves are divided into diaphragm type and piston type, with the same working principle. They are both powered by the pressure difference between upstream and downstream, and are controlled by a pilot valve to enable hydraulic differential operation of the diaphragm (piston), which is automatically adjusted by hydraulic pressure to open or close the main valve disc or be in a regulating state.

When the pressure water entering the control chamber above the diaphragm (piston) is discharged to the atmosphere or downstream low-pressure area, the pressure value acting on the lower part of the valve disc and below the diaphragm is greater than the pressure value above, thereby pushing the main valve disc to the open position. When the pressure value entering the control chamber above the diaphragm (piston) is between the inlet pressure and the outlet pressure, the main valve disc is in a regulating state, and its regulating position depends on the joint control of the needle valve and the guide valve in the conduit system.

The pilot valve can open or close its own small valve port by changing the downstream pressure, thereby changing the pressure value of the control chamber above the diaphragm (piston) and controlling the adjustment position of the main valve disc. Can be used for domestic water supply, fire protection systems, and industrial water supply systems.