Nina investigates how steam pumps move water uphill - with the help of Ollie, her smell neuron. Engineers Alec, Elia and Felix visit Nina in her workshop and discover that when people flush their toilets and empty their baths all the dirty water goes into a big underground pipe called a sewer. A pump moves the water up so it can be cleaned and steam keeps the pump moving.

Originally released by BBC Worldwide Learning, 2013. Streaming video file encoded with permission for digital streaming by Infobase on April 29, 2015.