Impulse turbines produce power when a jet of water from an enclosed diversion pipeline 'shoots' through a small nozzle directly onto the turbine runner. Impulse turbines are best for 'high head' sites (with 20 feet of head or more), but they do not require vey high flow rates. Pelton and Turgo turbines are two of the most common impulse turbine families. See also: Flow, Head, Head Loss, Pelton Turbine, Runner, Turgo Turbine