Flush toilets
by Chris Woodford. Last updated: July 9, 2012.
Toilet, lavatory, loo, water closet, WC, John,
crapper, can—it's amazing we have so many names for something we
care to talk about so little. Toilets are hardly the most glamorous
of inventions, but imagine trying to live without them.
About 40 percent of the world's people (some 2.6 billion of us) are in that unhappy position,
lacking even basic sanitation. At the opposite end of the scale, in Japan, people have amazing
electronic toilets that do everything from opening and closing the
lid automatically to playing music while you use them. Most of the
world's toilets are more modest than this, but they're still pretty
ingenious "machines." Let's take a closer look!
Photo: Like most new toilets, this low-flush model is designed to save water; the two buttons on top let you choose whether to flush with a large or a small amount. Exactly how much difference that will make to your water consumption varies from one household to another. An old-style flush toilet typically uses 13 liters (3.4 US gallons), where a low-flush model will use only 6 liters (1.6 US gallons) and some models use only 4.8 liters (1.3 US gallons). If you save 7 liters (1.8 US gallons) per flush and people in your home flush 10 times a day, you'll save at least 25,500 liters (6700 US gallons) per year. You'll save more or less depending on how many people there are in your household.
Flush and go
At first sight, toilets seem quite
simple: you have a waste pipe going through the floor and a tank of water
up above (called a cistern) waiting to flush into it when someone
pushes a button or pulls a lever or a chain. Most flush toilets are
purely mechanical: pull the chain and the cistern empties through the
force of gravity, washing the bowl clean for use again.
They are literally mechanical because they flush and refill using levers inside—and
levers are examples of what scientists call simple machines.
There's a little bit more to toilets than this. When you flush, the cistern
has to refill automatically from a kind of faucet on the
side and the refilling operation has to last just long enough to fill
the tank without making it overflow. The "hole in the ground"
is more sophisticated than it looks as well. You may have noticed
that toilets always have a little water in the bottom of them; even
when you flush them, they never empty completely. Some water is
always trapped in a big curved pipe at the base of the toilet known
as the S-bend (or S-trap). This little bit of water effectively seals off the
sewage pipe beneath it, stopping germs and bad smells from coming up
into your bathroom.
Photo: Lift the cistern on a toilet and this is what you'll find inside.
The cistern (upper tank of water) drains through a valve in the center through the force of gravity.
The blue, balloon-like object on the left is
a plastic float that drops when the water level falls.
This tilts the plastic lever (known as the ballcock) and allows the cistern to refill.
Who invented the flush toilet?
Although it's popularly believed that flush toilets were invented by an English plumber called
Thomas Crapper (c.1836–1910), it's an unhelpful myth, for two reasons: flushing toilets are an ancient technology and no single person can really claim to have invented them: dozens (if not hundreds) of different inventors have been involved in their development over the years,
especially since Crapper's lifetime. Archaeological evidence shows that primitive toilets using river water to flush wash away waste are over 5000 years old and date back to something like 3000BCE. The two inventors who have the best claim to our modern toilet-flushing system were born hundreds of years before Crapper. Among his many other achievements, prolific Arabic inventor and engineer Al-Jazari developed a flushing hand-washing device in 1206, while
English writer and courtier Sir John Harington (1561–1612) described a method for flushing a toilet in 1596 in his article A New Discourse of a Stale Subject, Called the Metamorphosis of Ajax.
Search through the invention records at the US Patent and Trademark Office and you'll find literally hundreds that relate to toilets and their flushing mechanisms. I've chosen two examples from 1874 to give you a flavor of what you can find. On the left (and drawn in plan view, from above), we have the self-disinfecting water-closet basin developed by Jabez Burns, Charles Higgins, and William Higgins ("Improvement in Water-Closet Basins", US Patent#149,195).
Their simple innovation was to make the pipe that fills the toilet basin squirt sideways over a bar of soap, thus
disinfecting the basin and stopping any smell. On the right, you can see Archibald McGilchrist's trap-less water closet ("Improvement in Water-Closet Apparatus", US Patent#157,211).
Unlike with an S-bend closet, there is no water trap to stop odors. Instead, the flush mechanism raises and lowers a ball-shaped
valve that seals the waste pipe. A rising and falling float (I've colored it green in the artwork) operates a valve mechanism (colored yellow) to refill the basin in the usual way. You can explore lots more similar inventions with a
search for "water closet" on Google Patents (it just gave me 13,000 results!).
Artwork: Two examples of 19th-century improvements in water closets (toilets) by American inventors.
Images courtesy of US Patent and Trademark Office with added coloring and annotations by Explainthatstuff.com.
Find out more
On this website
- Composting toilets: Learn about environmentally friendly toilets that don't waste water.
- Water pollution: How human waste can spoil the environment if we don't dispose of it carefully.
On other sites
- How Things Work/Flush Toilet: Here's an alternative explanation of flush toilets with some nice cutaway diagrams showing the mechanism inside very clearly.
- Toilet Flushing (at home): The Waterwise campaign explains how toilets waste vast amounts of water—and what you can do to make a difference.
- WaterAid: What if you had no toilet and no clean water? WaterAid is one of the groups working with people in developing countries to help them achieve the standard of living the rest of us take for granted.
Books about toilet history
Practical books
