The utility model relates to a groove type rail formula water conservation water tank belongs to public bath water conservation technical field. The utility model discloses a water tank, water tank feed water valve device, groove type rail, dog, slide bar, bottle lid, water -jug, control lever, flashing valve valve gap, drain valve device, ejector pin, footboard, groove type rail installs in the water tank, and water tank feed water valve device is installed in the water tank, and the water -jug is installed in groove type rail, and slide bar one end is connected with the water -jug, and the dog is installed on the slide bar other end, and the bottle lid is installed on the water -jug top, and the control lever is installed in the water -jug bottom, and the drain valve device is installed in the water tank, and the flashing valve valve gap lies in the outlet department of drain valve device and lies in the control lever lower part, and ejector pin one end is connected with the flashing valve valve gap other end, and the footboard is connected with the ejector pin other end. The utility model discloses make things convenient for drainage using water wisely again, the drainage impulsive force is big, and the suitability is strong, simple structure, low, the easy operation of cost investment.