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. A flush toilet may be euphemistically called a lavatory, a loo, a john or a water closet, abbreviated to "W.C."
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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.
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 parts of the following designs:
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, and Fluidmaster, founded in the United States by inventor Adolf Schoepe, makes them.
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.
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" (15 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 a few feet 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. A similar German expression is Wasser ziehen ("to pull water").
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 due to a change in regulations.
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 it 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 with flapper valves but due to EU harmonisation the regulations have changed. 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.
It can now be found in dual flush versions.
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 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. Newer toilets from several companies such as Kohler that are pressure-assisted use 1.4 US gallons (5.3 l) to 1.1 US gallons (4.2 l) per flush.
In 1906, William Sloan first made his "flushometer" style toilet flush valve, incorporating his patented design,[12] 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 urinals. Since they have no tank, they have zero recharge time, and can be used immediately by the next user of the toilet. 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, the flushometer mechanism closes the valve and stops the flow. 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 pounds per square inch (2.1 bar). 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).
A simple rotating bucket is located within the tank, that is lever activated manually.
The bowl, loo or pan, of a toilet is the receptacle that receives bodily waste. A toilet bowl is most often made of a ceramic, 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.
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 siphon 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.
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 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 ceramic toilets invented and since the early 1970s are now only found in a few localities such as in some parts of Germany.
In Germany, Netherlands, and some regions of Poland, the bowl is designed to hold the fecal matter out of the water prior to flushing by means of a receiver shelf, whereas most U.S. or U.K. designs immediately allow it to plunge into standing water. This reverse design prevents the occurrence of any splash-up which commonly happens when fecal matter plunges into the standing water in the standard designs (although substantial deposits may cause splash-up problems of their own). The disadvantage is that it also increases the associated odor and may require the use of a brush to remove bits of feces that may have "skid-marked" on the shelf. Similar designs are found in some early toilets in the U.S., one particular brand being labeled the "Grand Niagara", as the flushing of the shelf creates a waterfall effect into the drain chamber.
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 most Russian older style trains, made in Eastern Germany (Ammendorf factory, design dated probably to the 50s), employing a pan-like shutter valve discharging waste directly on the railway. The toilet usage is permitted only on the go, and outside of major cities. These toilets are currently vanishing, together with the old trains, being replaced with modern vacuum systems.
For a review of Japanese toilet usage and history, see Toilets in Japan.
Nowadays, there is a significant move towards using less water for flushing flush toilets. This has resulted in the emergence of new toilet designs and national standards on water consumption for flushing. In addition, some people are also modifying their existing flush toilets to use less water. This can be done by adding a floating weight (ie brick, water bottle) into the toilet's water tank. This allows the use of less water per flush since the water pressure is hence increased.[13] Other modifications are often done on the water system itself; ie by using greywater, or a system that pollutes the water more gradually, more efficient use of the water is accomplished.
Pre-1994 residential and pre-1997 commercial flush toilets use 3.4 US gallons (13 L) of water per flush (gpf or lpf). In 1992, the United States Congress passed the Energy Policy Act of 1992, which mandated that beginning in 1994 common flush toilets use only 1.6 US gallons (6.1 L).[14] In response to the Act, manufacturers produced low-flow toilets, which many consumers did not like because they often required more than one flush to remove solids. 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 1.3 US gallons (4.9 L) or less.[15] HETs may be single-flush or dual-flush. A dual-flush toilet permits its user to choose between two amounts of water.[16] 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 (250 grams of simulated fecal matter). 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.[15] 1.6 gpf toilets are also sometimes referred as ULF (Ultra Low Flow) toilets.
The term "water-closet" was an early term for a room with a toilet. Originally, the term "wash-down closet" was used.[17] The "water-closet" was invented in England around 1870. It did not reach the United States until the 1880s. Around this time, only luxury hotels and wealthy people had indoor private bathrooms. By 1890, the fear of the theory of disease was beginning to arise about carelessly disposed human waste being contaminated and infectious. This is stated in the book "A People and A Nation" the eighth edition. 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 in common North American usage. In the UK, the terms "bathroom" and "toilet" are used to indicate discrete functions, even though bathrooms in modern homes have been designed according to the American norm since around the mid-sixties. The term "water closet" was probably adapted because in the late 19th century, with the advent of indoor plumbing, a toilet displaced an early clothes closet, closets being shaped to easily accommodate the spatial needs of a commode.. Early indoor toilets had in fact been known as garderobes because they actually were used to store clothes, as the smell of ammonia was found to deter fleas and moths. 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" or "WC". The Royal Spanish Academy Dictionary accepts "váter" as a name for a toilet or bathroom, which is derived from the British term "water-closet". In French the expression "aller aux waters" ("to go to the waters") has now become obsolete, but it also derives from "water closet". "WC" is still used in the French language, although not as common as the term "toilet", and pronounced as "VC", a shortened version of "double V C". In Germany the expression "Klo" (first syllable of "closet") is still used, though the term is colloquial and not welcome in polite conversation.
In Germany, Belgium and the Netherlands (due to the bowl design (above)) the toilet is often kept in a separate room known as the "WC" even in newly built residences. In the Dutch-speaking part (Flanders) as well as the French-speaking part of Belgium (Wallonia) as well as Italy, "WC" is a frequently used synonym for "toilet".
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.[18]
Ordinary toilet cleaning is done by a toilet brush.
Clogging is a common problem of flush toilets. It usually occurs as a result of an attempt to flush unsuitable items, or too much toilet paper, although it can occur spontaneously due to limescale fouling of the drain pipe. Flushing hair should also be avoided. Clogging is particularly insidious, as it is usually not discovered immediately, but only later by an unsuspecting user trying to flush a loaded toilet. Overflowing of the water mixed with excrements may then occur, depending on the bowl volume, tank capacity and severity of clogging. For this reason, rooms with flush toilets should be designed as wet rooms, with a second drain on the floor, and a shower head capable of reaching whole floor area. Common means to remedy clogging include use of toilet plunger, drain cleaner or a plumber's snake.
Toilets in multi-story buildings, located on fire-resistance rated floors typically require at least two through-penetrations, which can compromise the rating of the floor if left untreated. One opening is for the fresh water supply to flush and/or fill the water tank. The other through-penetration is for the drain pipe. The fresh water supply line requires routine firestopping. The drain pipe, however, is exempt from firestopping in many building codes, particularly when noncombustible piping is used, because the penetration terminates on the unexposed side in a ceramic bowl filled with water, which can withstand significant fires. Intumescent firestops are often used, in the event plastic pipes are used for toilet drains, so that the melting plastic pipe is choked off in the event of an accidental fire. It is, however, customary to fill the metallic drain pipe annulus with rockwool packing. Even with the best of intentions, it would be difficult for the firestopper to install a sealant, because he is not allowed or inclined to remove the flange, which is what is partially used to support the drain pipe below during the installation process.
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