Every flush sends water on a hidden journey: through gentle sloping pipes, pumping stations, metal screens, calm tanks and trillions of hungry bacteria, until it is clean enough for a river. This animated explainer follows it all the way, from the trap under your toilet to London's 130-tonne fatberg and the city that drinks recycled water.

Chapters:

0:00 Intro

0:24 The flush: the first few seconds

1:10 The hidden river: sewers and pumping stations

2:04 The Great Stink: London, 1858

3:28 The monster: screens, wipes and fatbergs

4:42 The big settle: primary tanks

5:22 The tiny workers: bacteria and activated sludge

6:24 The final polish: clarifiers and UV

7:19 Power from sludge: digesters and biogas

8:16 Full circle: drinking it again

• Why toilets hold water in a U-bend, and how sewers run almost entirely on gravity

• The Great Stink of 1858 and Joseph Bazalgette's brick tunnels, still working today

• Wet wipes, fatbergs and the Whitechapel monster of 2017

• Settling tanks, activated sludge, clarifiers and UV disinfection

• Digesters that turn sludge into biogas and power, and Singapore's NEWater

• English AI voiceover, original synthesized music and SFX, mixed to -14 LUFS

• Original vector animation, 1080p 60 fps, fact-checked, family-friendly

A clean, fascinating look at one of the hidden machines that run our world.