1992

Low-Flow Toilet

Think about the ordinary toilet that you find in a typical home. It is a low-cost device that uses gravity as its sole power source, yet it is highly reliable, virtually indestructible, easy and inexpensive to maintain, and it solves a huge sanitation problem.

Each time you use a typical home toilet you press the flush lever. This pulls on a chain that opens a small rubber valve at the bottom of the tank. This valve costs four dollars and needs replacing perhaps every five years. With the valve open, all of the water in the tank rushes into the bowl in a few seconds.

Because of the design of the bowl and the passageway leading out of it, the inrush of water causes a siphon to form in the passageway. The siphon efficiently sucks everything out of the bowl.

Meanwhile, with the tank empty, the flapper valve has closed over the opening in the tank. A flotation valve has realized that the tank is empty, starting the flow of water into the tank and the bowl so that both refill. When the tank is full, the flotation valve will shut off the water automatically and the toilet is ready for its next use.

Think about the alternatives. You could be using an outhouse. Or you could use a bucket indoors and then empty it into a human waste compost pile in the backyard. Which actually is not the worst idea environmentally, provided you have the land and the patience to handle it. But in a thriving city, both of those options are non-starters. The flush toilet is a major society-wide convenience brought to us by engineers.

In 1992, the United States went through an interesting transition. The old standard was 3.5 gallons per flush. To decrease water consumption, the US mandated a 1.6-gallon flush. Engineers had to create bowl designs and flow patterns that would empty the bowl, without clogging, on much less water. They rose to the challenge. This one small change now saves the US billions of gallons of water per day.

SEE ALSO Pompeii (79), Plastic (1856), Modern Sewer System (1859).

In 1992, toilets in the United States changed their standards from 3.5 gallons per flush to 1.6.