Interior shots of large roller being lowered onto other rollers, of man lowering roller onto scale for weighing, of man turning knobs on panel, taking readings and walking away. Shot of three men hoisting rollers off pile of rollers with chainfall, lowering rollers on scale. Shot of superintendant of aqueduct finishing his rounds, taking two final readings, sitting down at his desk and telephoning. LACUs of operator at control panel. CUs of hands opening valves. Interior shots of pump room from high balcony, of chemist carrying out tests in laboratory. Several shots of water being treated.