The Economist’s cover story this week asks if we will ever again invent anything as useful as “the humble loo”. When we devoted a Big Question to the best inventions, it was also the one chosen by Nick Valéry

From INTELLIGENT LIFE magazine, January/February 2012

More even than the miracle of antibiotics, the flush toilet has done most to rid us of infectious disease. Without plumbed sanitation within the home to dispose of human waste, we would still be living in a brutal age of cholera, dysentery, typhus and typhoid fever—to say nothing of bubonic plague.

The flush toilet was invented, and re-invented, many times. Indoor toilets first appeared in the Indus Valley over 4,000 years ago. The Romans built their latrines over drains carrying running water that discharged into a fetid Tiber. Legend has it that Queen Elizabeth I was too embarrassed to use the flush toilet built for her by her godson, Sir John Harington, for fear that the roar of the rushing water would inform the palace of the royal bowels being evacuated.

But it is only in the past century and a half that the water closet has graced more humble abodes. After Prince Albert died of typhoid in 1861, a grief-stricken Queen Victoria demanded that piped water and sewage treatment be installed throughout Britain. A decade later, her son Prince Edward came close to dying of the same disease, and word about the need for flush toilets went out across the land. From Britain, it spread to France, and thence the rest of Europe and the world.

The father of the modern lavatory was not, as myth would have it, Thomas Crapper, whose name, in blue Gothic script, embellished the inside of many a Victorian lavatory bowl. If anyone can lay claim to the title, it is Alexander Cummings, a watchmaker in Bond Street, who was granted the first patent for a flush toilet in 1775. The popular toilets made by Crapper’s workshop in Chelsea were based on a later siphon design, patented in 1819 by an employee named Albert Giblin.

The lavatory has changed little since Crapper’s time. Water trapped in an S-shaped bend keeps the stench at bay, while allowing the waste to be siphoned off. Pulling a chain, or pressing a handle, opens a valve that causes water in a cistern to gush into the bowl. When it is empty, a floating ballcock closes the valve, and the tank refills under pressure from the water supply. Tweaks over the years have simplified the valve system and reduced the water needed. The flushing toilet still hasn’t reached everyone, but it has done billions a great service.

Do you agree? For more thoughts on the greatest inventions read Tom Standage on writing, Roger Highfield on the scientific method, Edward Carr on the blade, Samantha Weinberg on the internet and Nnaemeka Ikegwuonu on the transistor radio.

Nick Valéry writes a technology column for The Economist. He edited Intelligent Life when it was an annual, from 2004 to 2006

Picture credit Getty