Abstract: A flow measuring apparatus of an embodiment is provided that comprises a cylinder and a piston movable in the cylinder between first and second positions. The piston divides the cylinder's interior area into first and second portions. A biasing member urges the piston toward the first position. A first fluid passageway allows fluid to bypass the piston, and a second fluid passageway is in fluid communication with the first fluid passageway and with the first portion of the cylinder. The second fluid passageway provides fluid to the first portion of the cylinder to move the piston toward the second position. A flow diverter is movable between a first flow position that allows fluid to pass through the first fluid passageway to the outlet and a second flow position that causes fluid to flow into the second flow passageway and into the first portion of the chamber.