H142X model liquid pressure water line control valve, is a hydraulic control valve which auto control water box, water tower liquid levels. When wate line drop over preset value, float ball open, piston up chamber pressure reduce, up and down pistion have pressure drop, disc open to supply water under the pressure drop action; when water line up to preset height, float ball close, piston up and down chamber pressure increase constantly make disc close stop supplying water. So displacement auto control liquid levels's setted height, achieve function of auto water supply.