The original flush toilet is believed by many to be a tank-type model invented by a 16th century English poet named John Harington [source: Lienhard]. This device followed the same basic principles of the modern flush toilet in that there was a tank of water used to flush waste out of the bowl and, with any luck, through the drain lines. The main problem with this toilet was that few people had indoor plumbing during this time. Still, the invention was considered a smashing success. According to some experts, Harington even designed a version for Queen Elizabeth [source: Lienhard].
Tankless toilets debuted on the plumbing scene with the invention of the first flush valve toilet by Sloan Valve Company in 1906 [source: Sloan]. In this model, a valve controlled the flow of water with each flush, allowing a specific amount to pass from the supply line into the toilet fixture at a pressure sufficient enough to cleanse the bowl. Sloan's basic design was improved upon over the years, rising in popularity as indoor plumbing became widespread. Most tankless toilets still work using this same basic design.
The first tankless toilets didn't immediately transform the world of plumbing -- Sloan sold only three units in the first two years of production. But the popularity of these flush valve toilets continued to grow throughout the 20th century, particularly in industrialized areas. Sloan's tankless toilet became the model for commercial flushometers, a type of tankless toilet that is now by far the most common fixture in public restrooms throughout the Western world.
The tank-style toilet also underwent a redesign during 20th century. The massive migration that occurred during America's Industrial Age led to the construction of high-rise apartments in which space was a precious commodity. During this time, water tanks were moved to a perch on the wall several feet above the porcelain throne. The release of water from such a height made for an extremely powerful and cleansing flush. As it turns out, this was overkill. In the next section, we'll learn more about tank-style toilets, including the amount of water it takes to power their flush and how some early models paved the way for the use of tankless toilets in urban apartments.