A system curve is a curve used to display the relationship between the system's required head and its flowrate. Losses in a closed conduit system can be quantified by using the energy equation, shown below: 2 2 = 2 2 Where and are the pump (energy added) and turbine (energy removed) heads, respectively, and is the head loss. Normally, the losses are separated into friction losses and minor losses. Friction losses can be calculated using the Darcy-Weisbach equation = 2 2 Where f indicates friction factor. There are many ways friction factor can be obtained. One way is through the use of Moody Diagram, while other ways are through empirical equations. One such empirical equation is the Swamee-Jain equation shown below: = 0.25 [log10 (/ 3.7 5.74 Re0.9)] 2 Where is the material roughness, D is the pipe diameter, and Re is the Reynolds number, which is the following ratio: Re = Where is the fluid velocity, D is the pipe diameter, and is the fluid kinematic viscosity (for water, it's = 1 105 2/). If we neglect minor losses, the energy equation can be written as =