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Flush toilet

Close coupled cistern type flushing toilet.

A flush toilet is a toilet that disposes of human waste by using water to flush it through a drainpipe to another location. Flushing mechanisms are found more often on western toilets (used in the sitting position), but many squat toilets also are made for automated flushing. [1] Modern toilets incorporate an 'S','U', 'J', or 'P' shaped bend that causes the water in the toilet bowl to collect and act as a seal against sewer gases. Since flush toilets are typically not designed to handle waste on site, their drain pipes must be connected to waste conveyance and waste treatment systems.

Contents

History

Toilet with elevated cistern and chain attached to lever of discharge valve.

As with many inventions, the flush toilet was the result of a long development. Therefore, instead of a single name and date, there follows a list of significant contributions to the history of the device.

  • circa 26th century BC: Flush toilets were first used in the Indus Valley Civilization. The cities of Harappa and Mohenjo-daro had a flush toilet in almost every house, attached to a sophisticated sewage system. [2]
  • circa 18th century BC: Flush toilet constructed at Knossos on Minoan Crete[3]
  • circa 15th century BC: Flush toilets used in the Minoan city of Akrotiri.
  • 9th century BC: Flush toilets in Bahrain Island.[4]
  • 1st to 5th centuries AD: Flush toilets were used throughout the Roman Empire. Some examples include those at Vindolanda on Hadrian's Wall in Britain. With the fall of the Roman Empire, the technology was lost in the West.
  • 1596: Sir John Harington published A New Discourse of a Stale Subject, Called the Metamorphosis of Ajax, describing a forerunner to the modern flush toilet. The design had a flush valve to let water out of the tank, and a wash-down design to empty the bowl. He installed one for his godmother Elizabeth I of England at Richmond Palace, although she refused to use it because it made too much noise. The Ajax was not taken up on a wide scale in England, but was adopted in France under the name Angrez.
  • 1738: A valve-type flush toilet was invented by J. F. Brondel.
  • 1775: Alexander Cummings invented the S-trap (British patent no. 814?), still in use today, which uses standing water to seal the outlet of the bowl, preventing the escape of foul air from the sewer. His design had a sliding valve in the bowl outlet above the trap.
  • 1777: Samuel Prosser invented and patented the 'plunger closet'.
  • 1778: Joseph Bramah invented a hinged valve or 'crank valve' that sealed the bottom of the bowl, and a float valve system for the flush tank. His design was used mainly on boats.
  • 1819: Albert Giblin received British patent 4990 for the "Silent Valveless Water Waste Preventer", a siphon discharge system.
  • 1852: J. G. Jennings invented a wash-out design with a shallow pan emptying into an S-trap.
  • 1857: The first American patent for a toilet, the 'plunger closet', was granted.
  • 1860: The first watercloset installed on the European continent was imported from England. It was installed in the rooms of Queen Victoria in castle Ehrenburg (Coburg, Germany); she was the only one who was allowed to use it.
  • The first popularized water closets were exhibited at The Crystal Palace and these became the first public toilets. They had attendants dressed in white and customers were charged a penny for use. This is the origin of the phrase "To spend a penny".
  • 1880s: Thomas Crapper's plumbing company built flush toilets of Giblin's design. After the company received a royal warrant, Crapper's name became synonymous with flush toilets. Although he was not the original inventor, Crapper popularized the siphon system for emptying the tank, replacing the earlier floating valve system which was prone to leaks. Some of Crapper's designs were made by Thomas Twyford. The similarity between Crapper's name and the much older word crap is a coincidence.
  • 1885: Thomas Twyford built the first one-piece china toilet using the flush-out siphon design by J. G. Jennings.
  • 1886: An early jet flush toilet was manufactured by the Beaufort Works in Chelsea, England.
  • 1906: William Elvis Sloan invented the Flushometer, which used pressurized water directly from the supply line for faster recycle time between flushes. The original Royal Flushometer is still in use today in public restrooms worldwide.
  • 1907: Thomas MacAvity Stewart of Saint John, New Brunswick patented the vortex-flushing toilet bowl, which creates a self cleansing effect.[5]
  • 1980: Bruce Thompson, working for Caroma in Australia, developed the Duoset cistern with two buttons and two flush volumes as a water-saving measure. Modern versions of the Duoset are now available worldwide, and save the average household 67% of their normal water usage.[6]

Flushing mechanisms

The flushing mechanism provides a large flow of water into the bowl (which is described later in this article). The mechanism usually incorporates one or more elements of the following designs:

Tank fill valves

Tank fill valves are found in all tank-style toilets. The valves are of two main designs: the side-float design and the concentric-float design. The side-float design has existed for over a hundred years. The concentric-design has only existed since 1957, but is gradually becoming more popular than the side-float design. The concentric design fill valve is manufactured primarily by the Fluidmaster company, founded in the United States by inventor Adolf Schoepe.

The side-float design incorporates a float, usually ball-shaped, which is located to one side of the main valve tower at the end of a rod or arm. As the side-float rises, so does the side-float-arm. The arm is connected to a linkage which blocks the water flow into the toilet tank, and thus maintains a constant level in the tank.

The newer concentric-float fill valve consists of a tower which is encircled by a plastic float assembly. Operation is otherwise the same as a side-float fill valve, even though the float position is somewhat different. By virtue of its more compact layout, interference between the float and other obstacles (tank insulation, flush valve, and so on) is greatly reduced, thus increasing reliability. The concentric-float fill valve is also designed to signal to users automatically when there is a leak in the tank, by making much more noise when a leak is present than the older style side-float fill valve, which tends to be nearly silent when a slow leak is present.

Tank style with flapper-flush-valve

In a tank-based system, the storage tank (or cistern) collects between 6 and 17 liters of water over a period of time. This system is suitable for locations plumbed with 1/2" (12 mm) or 3/8" (10 mm) water pipes. The storage tank is kept full by a tank fill-valve. The storage tank is usually mounted directly upon the bowl, although some tanks are mounted on the wall above the bowl in an attempt to increase the flush water pressure as it enters the bowl. Tanks near the ceiling are flushed by means of a dangling pull chain, often with a large ornate handle, connected to a flush lever on the cistern itself. "Pulling the chain" remains a British euphemism for flushing the toilet, although this type of tank or cistern is becoming rare.

In tanks using a flapper-flush-valve, the outlet at the bottom of the tank is covered by a buoyant plastic cover or flapper, which is held in place against a fitting (the flush valve seat) by water pressure. To flush the toilet, the user pushes a lever, which lifts the flush valve from the valve seat. The valve then floats clear of the seat, allowing the tank to empty quickly into the bowl. As the water level drops, the floating flush valve descends back to the bottom of the tank and covers the outlet pipe again. This system is common in homes in the USA and in continental Europe. Recently this flush system has also become available in the UK.

Tank style with siphon-flush-valve

This system, invented by Albert Giblin and common in the UK, uses a storage tank similar to that used in the flapper-flush-valve system above. This flush valve system is sometimes referred to as a valveless system, since no traditional type of valve is required. Some would argue, however, that any system of regulating the flow of a fluid is still technically a valve. In the siphon-flush-valve system, the user pushes a lever or button, forcing the water up into the tank siphon passageway which then empties the water in the tank into the bowl. The advantage of a siphon over the flush valve is that is has no sealing washers that can wear out and cause leaks, so it is favoured in places where there is a need to conserve water. Until recently, the use of siphon-type cisterns was mandatory in the UK to avoid the potential waste of water by millions of leaking toilets. These valves can sometimes be more difficult to operate than a "flapper"-based flush valve because the lever requires more torque than a flapper-flush-valve system. This additional torque required at the tank lever is due to the fact that a user must forcefully lift a certain amount of water up into the siphon passageway in order to initiate the siphon action in the tank.

Older installations, known as "high suite combinations", used a high-level cistern (tank), fitted above head height, that was operated by pulling a chain hanging down from a lever attached to the cistern. When more modern close-coupled cistern and bowl combinations were first introduced, these were first referred to as "low suite combinations". Modern versions have a neater-looking low-level cistern with a lever that the user can reach directly, or a close-coupled cistern that is even lower down and integrated with the bowl. In recent decades the close coupled tank/bowl combination has become the most popular residential system, as it has been found by ceramic engineers that improved waterway design is a more effective way to enhance the bowl's flushing action than high tank mounting.

Tank style with high-pressure or pressure-assist valve

This system utilizes mains water pressure to pre-pressurize a plastic tank located inside of what otherwise appears to be the more typical ceramic flush tank. A flush cycle begins each time a user flushes the bowl. After a user flushes and the water in the pre-pressurized tank has finished emptying into the bowl, the outlet valve in the plastic tank shuts. Then the high pressure water from the city main refills the plastic tank. Inside the tank is an air-filled balloon-like rubber diaphragm. As the higher-pressure mains water enters the tank, the rubber diaphragm is also pressurized and shrinks accordingly. During flushing, the compressed air inside of the diaphragm pushes the water into the bowl at a flow rate which is significantly higher than a tank style gravity-flow toilet. This system requires slightly less water than a gravity-flow toilet. Pressure-assist toilets are sometimes found in both private (single, multiple and lodging) bathrooms as well as light commercial installations (such as offices). They seldom clog, but the pressurized tanks require replacement about once every 10 years. They also tend to be noisier - a concern for residential settings. The inner bowl stays cleaner (in appearance) than gravity counterparts because of the larger water surface area and the toilet's forceful flush.

Tankless style with high-pressure (flushometer) valve

In 1906, William Sloan first made his "flushometer" style toilet flush valve, incorporating his patented design, available to the public. The design proved to be very popular and efficient, and remains so to this day. Flushometer toilet flush valves are still often installed in commercial restrooms, and are frequently used for both toilets and for urinals. They can be easily identified by their distinctive chrome pipe-work, and by the absence of a toilet tank or cistern, wherever they are employed.

Some flushometer models require the user to either depress a lever or press a button, which in turn opens a flush valve allowing mains-pressure water to flow directly into the toilet bowl or urinal. Other flushometer models are electronically triggered, using an infrared sensor to initiate the flushing process. Typically, on electronically triggered models, an override button is provided in case the user wishes to manually trigger flushing earlier. Some electronically triggered models also incorporate a true mechanical manual override which can be used in the event of the failure of the electronic system. In retrofit installations, a self-contained battery-powered or hard-wired unit can be added to an existing manual flushometer to flush automatically when a user departs.

Once a flushometer valve has been flushed, and after a preset interval, inside the flushometer valve a pneumatic mechanism closes the valve. The flushometer system requires no storage tank, but requires a high volume of water in a very short time. Thus a 3/4 inch (19 mm) pipe at minimum, or preferably a 1 inch (25 mm) pipe, must be used, but as the high volume is used only for a short duration, very little water is used for the amount of flushing efficacy delivered. Water main pressures must be above 30 psi. While the higher water pressure employed by a flushometer valve does scour the bowl more efficiently than a gravity-driven system, and while fewer blockages typically occur as a result of this higher water pressure, flushometer systems still require approximately the same amount of water as a gravity system to operate (1.6 gpf).

Bowl designs

The bowl, loo or pan, of a toilet is the receptacle that receives bodily waste. A toilet bowl is most often made of porcelain, but can sometimes be made of stainless steel or composite plastics. Toilet bowls are mounted in any one of three basic manners: above-floor mounted (pedestal), wall mounted (cantilever), or in-floor mounted (natural position).

Within the bowl, there are three main water-way design systems: the siphoning trapped system (found primarily in North American residential installations, and in North American light commercial installations), the non-siphoning trapped system (found in most other installations both inside and outside of North America), and the valve-closet system (found in many specialty applications, such as in trains, planes, buses, and other such installations around the world). Older style toilets called "washout" toilets are now only found in a few locations.

Siphoning-toilets

The siphoning-toilet is perhaps the most popular design in North America for residential and light commercial toilet installations. Some other terms for these types of toilets are "siphon jet", "siphon wash", and in North America, "wash down". All siphoning-toilets incorporate an 'S' shaped water-way. The water-ways in these toilets are designed with slightly smaller diameters than a non-siphoning toilet, so that the water-way will naturally fill up with water, each time it is flushed, thus creating the siphon action. To flush the toilet the user activates a flushing mechanism (see above), which pours a large quantity of water quickly into the bowl. This creates a flow large enough to purge the bowl's water-way of all air, thus causing the bowl to empty rapidly due to the siphonic action that has been created. This flow stops as soon as the water level in the bowl drops below the first bend of the siphon, allowing air to enter the S-pipe to break the column of liquid and to halt the siphonic action.

A "true siphoning-toilet" can be easily identified by the noise it makes. If it can be heard to suck air down the drain at the end of a flush, then it is a true siphoning toilet. If not, then it is a non-siphoning toilet.

Non-siphoning toilets

The bowl drain water-way is at the rear of the bowl and is connected to the waste pipe. In American designs the water-way discharge is situated between the rear floor-mount bolts of an extended base. Useful Reference Encyclopedia here it is directly bolted to a drain flange beneath the toilet. Thus it is hidden from view.

Most other toilet installations outside of North America are not designed to siphon, and instead rely on a reduced amount of water in the bowl combined with a rapid flushing action in order to completely clear the bowl of its contents after each flush. Wall-mounted flushometer fed toilets everywhere are also non-siphoning. Outside of North America, non-siphoning toilets are most commonly referred to as "washdown" toilets.









Valve closet

The valve closet has a valve or flap at the exit of the bowl with a water-tight seal to retain a pool of water in the pan. When the toilet is flushed, the valve is opened and the water in the pan flows rapidly out of the bowl into the drains, carrying the waste with it.

The earliest type of toilet, the valve closet is now scarce as a water-flush toilet. More complicated in design than other water closets, reliability is lower and maintenance more difficult. The most common use for valve closets is now in portable closets for caravans, camping, trains, and aircraft where the flushing fluid is recycled. This design is also used in train carriages in areas where the waste is allowed to be simply dumped between the tracks (the flushing of such toilets is generally prohibited when the train is in a station).

Washout toilets

Washout toilets have a shallow pool of water into which waste is deposited, with a trapped drain just behind this pool. Waste is cleared out from this pool of water by being swept over into the trap (usually either a P-trap or an S-trap) and then beyond into a sewer by water from the flush. Washout pans were amongst the first types of porcelain toilets invented and since the early 1970s are now only found in a few localities such as in some parts of Germany.

Cultural variations

Anglo-Indian toilet

In India, the "Anglo-Indian" design allows the same toilet to be used in the sitting or the squatting position. This type of toilet is also used on all Russian trains.

For a review of Japanese toilet usage and history, see Toilets in Japan.




US standards for low-flow and high-efficiency toilets

A pre 1994 flush-toilet or gravity-fed toilet uses 13 litres (3.4 US gallons or 2.8 imperial gallons) or more per flush. In 1992, the United States Congress passed the Energy Policy Act of 1992, which mandated that, from 1994, the common flush-toilet use only 1.6 US gallons (6 litres) of water per flush. In response to the Act, manufacturers produced low-flow toilets, which many consumers did not like. Manufacturers responded to consumers' complaints by improving the toilets. The improved products are generally identified as high efficiency toilets or HETs. HETs possess an effective flush volume of 4.8 litres (1.28 US gallons) or less.[7] HETs may be single-flush or dual-flush. A dual-flush toilet permits its user to choose between two amounts of water.[8] Some HETs are pressure-assisted (or power-assisted or pump-assisted or vacuum-assisted). The performance of a flush-toilet may be rated by a Maximum Performance (MaP) score. The low end of MaP scores is 250. The high end of MaP scores is 1000. A toilet with a MaP score of 1000 should provide trouble-free service. It should remove all waste with a single flush; it should not plug; it should not harbor any odor; it should be easy to keep clean. The United States Environmental Protection Agency uses a MaP score of 350 as the minimum performance threshold for HETs.[7] 1.6 gpf toilets are also sometimes referred as ULF toilets (or Ultra Low Flow) toilets.

Miscellaneous

Toilet trivia

Water-closet (WC), the name

The term "water-closet" was the original term for a room with a toilet. Originally, the term "bath-room" referred only to the room where the bathtub was located, which was usually a separate room, but this connotation has changed. The term "water closet" was probably adapted because in the late 1800's, with the advent of indoor plumbing, many a toilet displaced many an early clothes closet, closets being shaped to easily accommodate the spatial needs of a commode. The term "water closet" is still used today in some places, but it often refers to a room that has both a toilet and other plumbing fixtures such as a sink or a bathtub. Plumbing manufacturers often use the term "water-closet" to differentiate toilets from urinals. American plumbing codes still refer to a toilet as a "Water Closet" or a "WC". Many South American countries refer to a toilet as a "Water" which is now a term commonly found in Spanish dictionaries, and which derives from the British term "Water Closet".

Swirl direction

It is a commonly held misconception that when flushed, the water in a toilet bowl swirls one way if the toilet is north of the equator and the other way if south of the equator, due to the Coriolis effect - usually, counter clockwise in the northern hemisphere, and clockwise in the southern hemisphere. In reality, the direction that the water takes is much more determined by the direction that the bowl's rim jets are pointed, and it can be made to flush in either direction in either hemisphere by simply redirecting the rim jets during manufacture. On the scale of bathtubs and toilets, the Coriolis effect is too weak to be observed except under laboratory conditions. [9]

Toilet repairs

Manually filling the bowl

If the flush mechanism should fail in any toilet, the bowl contents can still be flushed out by quickly emptying a large bucket of two or three gallons of water into the bowl all at once. A domestic hose pipe will not work, as it cannot supply water fast enough to fill the siphon tube.

Flush tank repair

For flapper-flush-valve style toilets found mostly in North America, if the handle should have to be held down to achieve a complete flush an adjustment might need to be made in the handle-float-stopper mechanism. The handle of a toilet is typically attached to a stopper via a chain. A float is attached to the chain between the handle lever and the stopper. The float acts as a counter-balance to allow a certain amount of water to escape through the flush hole in the tank. The float mechanism on the chain should be some distance under the water level of the tank so it can keep the stopper open during a flush until the tank level reaches a certain level. At a certain level the float will pop to the top of the water and the stopper will close. The float should be at a position on the chain where it is under water and does not have so much buoyancy to allow water to leak through the stopper.

For siphon-flush-valve style toilets found mostly in the UK, the siphon's hidden, oblong, plastic diaphragm will tend to split and crack after approximately 10 years. The effectiveness of the flush can deteriorate suddenly or gradually as the cracking increases. This will often prompt owners to replace much of the system. However, the diaphragms are of a standard design and are inexpensive (50p) and simple to replace. Inside the cistern, unhooking the flush-handle's s-link allows the plunger and diaphragm to be removed, once the lower part of the siphon is unscrewed (it is not necessary to remove the whole assembly with some multiple part siphons -- the main outlet pipe can be left in place. Most are one piece and require removing from the cistern completely. There is also a small rubber diaphragm in the ballcock inlet assembly, which can deteriorate over a period of around 10 years -- if adjusting the water level becomes problematic, it is worth changing this inexpensive diaphragm.

Related

  • Ecological sanitation
  • Low flush toilet
  • Plumbing
  • Plumbing fixtures
  • Squat toilet
  • Toilet
  • Toilet rim block
  • Toilets in Japan
  • Urinal
  • Washroom

References

  1. ^ "Flushing squat toilets", naturesplatform.com
  2. ^ Rodda, J. C. and Ubertini, Lucio (2004). The Basis of Civilization - Water Science? pg 161. International Association of Hydrological Sciences (International Association of Hydrological Sciences Press 2004).
  3. ^ C. Michael Hogan. 2007. Knossos fieldnotes, The Modern Antiquarian
  4. ^ Sulabh International Museum of Toilets
  5. ^ Mario Theriault, Great Maritme Inventions 1833-1950, Goose Lane Editions, 2001, p. 34.
  6. ^ 100 Years of Australian Innovation - Dual flush technology
  7. ^ a b Testing of Popular Toilet Models by Veritec Consulting
  8. ^ "Low-flow revolution: As water concerns rise, toilet makers meeting the challenge", Lacrosse Tribune, 26 November 2007; accessed 3 January 2009
  9. ^ "Do bathtubs drain counterclockwise in the Northern Hemisphere?", The Straight Dope, April 15, 1983]

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