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Water Closet: A Fancy Name for a Toilet...

We see and use water closets everyday of our lives, whether at home, at work or out and about. In fact, according to the average person spends about 1.5 years on the "John" during the course of their lives. So this begs to question, how is it that we know so little about about a device we spend so much time with? Here are a few key facts about the "throne".

Tank Type Water Closet

Who Invented it and When?

The following quoted excerpts are from

"The first modern flushable toilet was described in 1596 by Sir John Harington, an English courtier and the godson of Queen Elizabeth I."

This device would be the first time anything similar to what we know today was invented. I'm going to assume this is why it's called the "John". Over the course of history, improvements were made. One of the most important, the trap, was developed almost 200 years later!

"In 1775 English inventor Alexander Cumming was granted the first patent for a flush toilet. His greatest innovation was the S-shaped pipe below the bowl that used water to create a seal preventing sewer gas from entering through the toilet."

And finally manufactured as a standard fixture by....

"In the late-19th century, a London plumbing impresario named Thomas Crapper manufactured one of the first widely successful lines of flush toilets. Crapper did not invent the toilet, but he did develop the ballcock, an improved tank-filling mechanism still used in toilets today. Crapper’s name would become synonymous with the devices he sold (although the English word “crap” predates him by centuries), thanks in part to American servicemen stationed overseas during World War I. These doughboys, unfamiliar with the relatively new-fangled invention, referred to the toilets as “crappers”—due to the Crapper brand’s ubiquity in England and France—and brought the term back home with them after the war."

There you have it!

What Kinds are There and How Do They Work?

Believe it or not, there are numerous types of water closets around the world. In fact, if you were to travel to a far eastern country, you might not even recognize them! To keep things relevant, we'll concentrate on the most common commercially used fixtures.

Generally water closets can be classified as either wall hung or floor mounted. Each type has its advantages and disadvantages. Wall hung toilets require carriers as well as chases behind the fixture for the carrier to reside. This can drive the overall cost of installation upwards. On the flip side, they are much easier to clean around, which makes the cost worth it when dealing with high traffic, high volume restrooms. Floor mounted models will work just fine if space is tight and usage is low to moderate.

Flushing Technology

The flushing mechanism of the water closet is composed of two variables:

  • The method of initiation

  • The method of evacuation


There are three major forms of initiating the flush; either by gravity via raised tank, a pressurized bladder (pressure assisted) or by a flush valve (flushometer). Gravity tank toilets are the most inexpensive, but also provide the lightest flushing action. This is due to the flow rate of the water being a function of purely gravity. Pressure assisted toilets have a water balloon type bladder which expands due to the water pressure in building when filling. When the bladder is opened, gravity and pressure combine to increase the flow-rate as well as flushing capacity. Finally the flush valve is simply what it's name implies, a valve! When opened, the pressurized water from the building's water main enters the bowl and evacuation ensues.

tank types

flush valve or flushometer

Gravity tanks are cheaper than pressure assisted tanks which are cheaper than flush valve applications (not always, but as a basic rule of thumb). In terms of duty, they can be thought of in the same order as listed above from light to heavy. The flush valve is recommended for most commercial applications for its ease of maintenance and high flushing capacity. Basically it's cheaper to operate since clogging is minimized and repair is fast.


Just like with initiation methods, there are three major forms of evacuation technologies, siphon jet, wash-down and blow-out. Siphon jet fixtures introduce water to the trapway as well as the rim. The majority of the water is introduced to the trapway which in turn generates a siphon and sucks the waste down the drain line. The water introduced to rim is mostly for rinsing but does assist in pushing the waste through the trap. The design of the trap keeps high water levels and thus cleaner bowls.

Wash-down fixtures introduce all or a majority of the water at the rim and push the waste out of the bowl and through the trap. Once flow is initiated, a siphoning action through the trap way assists in evacuation.

Finally, the blowout design introduces a large volume of high velocity water from the rim of the fixture. The geometry of the bowl results in the clean water literally "blowing" the waste out of the rear of the fixture.

siphon type and washdown


The flushing capacity of these technologies depends on the initiation device as well as the manufacturer's bowl design. In a commercial application siphon jet, wash-down and blowout will all produce good results with a properly selected flushometer. Blowout fixtures will usually provide the highest level of evacuation and are generally seen in very high capacity applications such as sports arena's or concert venues.

When Should You Use Each Type?

Here is strictly our recommendation:

  1. Residential:

  2. Floor mounted flush-tank, siphon jet

  3. Hotels, Motels:

  4. Floor mounted flush tank but preferably pressure assist or flushometer to minimize clogging, siphon jet or wash-down.

  5. Light Commercial:

  6. Floor or wall mounted pressure assisted or flushometer siphon jet or wash-down.

  7. Commercial, Educational, Healthcare:

  8. Wall mounted flushometer siphon jet

  9. Assembly:

  10. Wall mounted, flushometer blowout

Again, above is a suggestion, make your selection based on your project requirements.

What Makes a Fixture ADA Compliant?

In order for a fixture to be in compliance with the Americans with Disabilities Act, the height of the water closet must be between 17" to 19". This is a minimum of 2" higher than the standard height fixture. Keep in mind that the the seat and flushing initiation device must also be ADA compliant. In addition to the trim and fixture, the stall or restroom also must meet specific specifications.


As you can see, quite a lot goes into the design and selection of a water closet. Who would of thought such an unassuming ubiquitous item could be so technical? Hopefully you found this helpful, if you have any other questions feel free to contact us. Also be sure to check out our entire portfolio of plumbing design services here.

Water Closets, Smarter...

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