Abstract: A regulatable flush valve for tank type flush toilets includes a piston-cylinder dash pot, a weighted (fluid filled) plug/valve, a cylindrical overflow tube and a fluid vortex generating element secured in a coaxial arrangement vertically above the outlet of the toilet tank. The piston and plug/valve secured to the overflow tube are lifted from a normally closed position by a conventional pivoting handle mechanism. The piston-cylinder dash pot determines the water volume of a particular flush by controlling the rate of descent of the weighted plug/valve. The vortex generating element works in combination with the walls of the raised plug/valve to generate an energetic fluid vortex as the water flows from the tank into the toilet bowl. The vortex generated by the generating element is complementary to vortex generating elements within the toilet basin to increase washing action in the toilet bowl. The above combination of elements significantly reduces the volume of water required for complete flushing action.