Trap (plumbing)

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Water seal in drain pipe under a sink. Water enters at right, fills the trap, and continues left. Inverted siphoning occurs below the line "A". Annotated plumbing trap.jpg
Water seal in drain pipe under a sink. Water enters at right, fills the trap, and continues left. Inverted siphoning occurs below the line "A".
Examples of traps Vattenlaas.png
Examples of traps

In plumbing, a trap is a U-shaped portion of pipe designed to trap liquid or gas to prevent unwanted flow; most notably sewer gases from entering buildings while allowing waste materials to pass through. In oil refineries, traps are used to prevent hydrocarbons and other dangerous gases and chemical fumes from escaping through drains. In heating systems, the same feature is used to prevent thermo-siphoning which would allow heat to escape to locations where it is not wanted. Similarly, some pressure gauges are connected to systems using U bends to maintain a local gas while the system uses liquid. For decorative effect, they can be disguised as complete loops of pipe, creating more than one U for added efficacy.

Contents

General description

In domestic applications, traps are typically U, S, Q, or J-shaped pipe located below or within a plumbing fixture. An S-shaped trap is also known as an S-bend. It was invented by Alexander Cumming in 1775 but became known as the U-bend following the introduction of the U-shaped trap by Thomas Crapper in 1880. The U-bend could not jam, so, unlike the S-bend, it did not need an overflow. In the United States, traps are commonly referred to as P-traps. It is the addition of a 90 degree fitting on the outlet side of a U-bend, thereby creating a P-like shape (oriented horizontally). It is also referred to as a sink trap because it is installed under most sinks.

Because of its shape, the trap retains some water after the fixture's use. This water creates an air seal that prevents sewer gas from passing from the drain pipes back into the building. Essentially all plumbing fixtures including sinks, bathtubs, and showers must be equipped with either an internal or external trap. Toilets almost always have an internal trap.

A bottle trap, which can be unscrewed for cleaning Bottle trap, Van Nostrand's engineering magazine (1882).jpg
A bottle trap, which can be unscrewed for cleaning

Because it is a localized low-point in the plumbing, sink traps also tend to capture small and heavy objects (such as jewellery or coins) accidentally dropped down the sink. Traps also tend to collect hair, sand, food waste and other debris and limit the size of objects that enter the plumbing system, thereby catching oversized objects. For all of these reasons, most traps may be disassembled for cleaning or provide a cleanout feature.

Where a volume of water may be rapidly discharged through the trap, a vertical vented pipe called a standpipe may be attached to the trap to prevent the disruption of the seal in other nearby traps. [1] The most common use of standpipes in houses is for clothes washing machines, which rapidly dispense a large volume of wastewater while draining the wash and rinse cycles. [2]

In chemical engineering applications, a trap may be known as a lute. [3]

History

Wash-out closet, manufactured by Myers Sanitary Depot, New York, 1890 Text-book of hygiene; a comprehensive treatise on the principles and practice of preventive medicine from an American stand-point (1890) (14759841996).jpg
Wash-out closet, manufactured by Myers Sanitary Depot, New York, 1890

An S-shaped trap is also known as an S-bend. It was invented by Alexander Cumming in 1775 but became known as the U-bend following the introduction of the U-shaped trap by Thomas Crapper in 1880. The new U-bend could not jam, so, unlike the S-bend, it did not need an overflow.

Once invented, despite being simple and reasonably reliable, widespread use was slow coming. In Britain, the requirement to use traps was introduced only after the Great Stink in London, in the summer of 1858, when the objectionable smell of the River Thames, which was effectively an open sewer, affected the nearby Houses of Parliament. That motivated the legislators to authorise the construction of a modern sewerage system in the city, of which the S-bend was an essential component. As of 2017, only about two-thirds of the world population have access to traps,[ citation needed ] in spite of the evidence that good sewage systems significantly improve economic productivity in places that employ them. [4]

Venting and auxiliary devices

Trap with copper drain pipe at underside of firestop packing in two-hour fire-resistance rated concrete floor slab Trap firestop.jpg
Trap with copper drain pipe at underside of firestop packing in two-hour fire-resistance rated concrete floor slab
Typical P-trap P-trap.svg
Typical P-trap

Maintaining the water seal is critical to trap operation; traps might dry out, and poor venting can suction or blow water out of the traps. This is usually avoided by venting the drain pipes downstream of the trap; by being vented to the atmosphere outside the building, the drain lines never operate at a pressure much higher or lower than atmospheric pressure. In the United States, plumbing codes usually provide strict limitations on how far a trap may be located from the nearest vent stack.

When a vent cannot be provided, an air admittance valve may be used instead. These devices avoid negative pressure in the drain pipe by venting room air into the drain pipe (behind the trap). A "Chicago Loop" is another alternative.

When a trap is installed on a fixture that is not routinely used—such as a floor drain—the eventual evaporation of the water in the trap must be considered. In these cases, a trap primer may be installed; these are devices that automatically recharge traps with water to maintain their water seals.

Accepted traps in the United States

In some regions of the US, "S" traps are no longer accepted by the building codes as unvented S-traps tend to siphon dry. It may be possible to determine whether a household uses an S- or U-bend by the presence of an overflow pipe outlet.[ clarification needed ] What is required instead is a P-trap with proper venting. Certain drum-styled traps are also discouraged or banned. [5]

See also

Related Research Articles

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Plumbing is any system that conveys fluids for a wide range of applications. Plumbing uses pipes, valves, plumbing fixtures, tanks, and other apparatuses to convey fluids. Heating and cooling (HVAC), waste removal, and potable water delivery are among the most common uses for plumbing, but it is not limited to these applications. The word derives from the Latin for lead, plumbum, as the first effective pipes used in the Roman era were lead pipes.

<span class="mw-page-title-main">Flush toilet</span> Toilet that uses water to convey human waste down a pipe

A flush toilet is a toilet that disposes of human waste by using the force of water to channel it through a drainpipe to another location for treatment, either nearby or at a communal facility. Flush toilets can be designed for sitting or squatting, in the case of squat toilets. Most modern sewage treatment systems are also designed to process specially designed toilet paper. The opposite of a flush toilet is a dry toilet, which uses no water for flushing.

<span class="mw-page-title-main">Sanitary sewer</span> Underground pipe for transporting sewage

A sanitary sewer is an underground pipe or tunnel system for transporting sewage from houses and commercial buildings to a sewage treatment plant or disposal.

A drain cleaner or opener is a person, device or product unblocking sewer pipes or clogged wastewater drains. The term usually refers to a chemical or mechanical utensil such as a commercial chemical product, plumber's snake, drain auger or toilet plunger. Occasionally, it is applied to a plumber or another individual who performs the drain cleaning and hygiene.

<span class="mw-page-title-main">Storm drain</span> Infrastructure for draining excess rain and ground water from impervious surfaces

A storm drain, storm sewer, surface water drain/sewer, or stormwater drain is infrastructure designed to drain excess rain and ground water from impervious surfaces such as paved streets, car parks, parking lots, footpaths, sidewalks, and roofs. Storm drains vary in design from small residential dry wells to large municipal systems.

<span class="mw-page-title-main">Tap (valve)</span> Valve controlling the release of a liquid or gas

A tap is a valve controlling the release of a fluid.

A plumbing fixture is an exchangeable device which can be connected to a plumbing system to deliver and drain water.

<span class="mw-page-title-main">Drain-waste-vent system</span> Plumbing fixture

A drain-waste-vent system is the combination of pipes and plumbing fittings that captures sewage and greywater within a structure and routes it toward a water treatment system. It includes venting to the exterior environment to prevent a vacuum from forming and impeding fixtures such as sinks, showers, and toilets from draining freely, and employs water-filled traps to block dangerous sewer gasses from entering a plumbed structure.

<span class="mw-page-title-main">Sewer gas</span> Gases produced and collected in sewer systems

Sewer gas is a complex, generally obnoxious smelling mixture of toxic and nontoxic gases produced and collected in sewage systems by the decomposition of organic household or industrial wastes, typical components of sewage.

<span class="mw-page-title-main">Street elbow</span>

A street elbow is a type of plumbing or piping fitting intended to join a piece of pipe and another fitting at an angle. The difference between a street elbow and a regular elbow is the gender of its two connections.

<span class="mw-page-title-main">Air gap (plumbing)</span>

An air gap, as related to the plumbing trade, is the unobstructed vertical space between the water outlet and the flood level of a fixture. Air gaps of appropriate design are legally required by water health and safety regulations in many countries. An air gap is the simplest form of a backflow prevention device.

A vacuum breaker is a device that prevents water from being siphoned backward in a direction it is not desired to go. They are commonly placed on a bibcock valve or toilet or urinal flush valve, in which application they can prevent hose or drainage water from back-siphoning into the public drinking water system. This prevents contamination should the public drinking water system's pressure drop. A vacuum breaker is also used in steam distribution systems to prevent collapse of steam coils and pipes by letting in air when the pipe pressure becomes sub-atmospheric.

<span class="mw-page-title-main">Uniform Plumbing Code</span>

Designated as an American National Standard, the Uniform Plumbing Code (UPC) is a model code developed by the International Association of Plumbing and Mechanical Officials (IAPMO) to govern the installation and inspection of plumbing systems as a means of promoting the public's health, safety and welfare.

<span class="mw-page-title-main">Piping and plumbing fitting</span> Connecting pieces in pipe systems

A fitting or adapter is used in pipe systems to connect sections of pipe or tube, adapt to different sizes or shapes, and for other purposes such as regulating fluid flow. These fittings are used in plumbing to manipulate the conveyance of fluids such as water for potatory, irrigational, sanitary, and refrigerative purposes, gas, petroleum, liquid waste, or any other liquid or gaseous substances required in domestic or commercial environments, within a system of pipes or tubes, connected by various methods, as dictated by the material of which these are made, the material being conveyed, and the particular environmental context in which they will be used, such as soldering, mortaring, caulking, plastic welding, welding, friction fittings, threaded fittings, and compression fittings.

A trap primer is a plumbing device or valve that adds water to traps. The water seals in traps are needed to prevent sewer gases from entering buildings, but because this water is exposed to the air, it is subject to evaporation over time in infrequently used floor drains, leading to the release of sewer gas into the environment. The trap primer mitigates this problem by injecting water, either directly or indirectly, into the trap to maintain the water seal indefinitely.

<span class="mw-page-title-main">Grease trap</span> Trap designed to intercept most greases and solids before they enter a wastewater disposal system

A grease trap is a plumbing device designed to intercept most greases and solids before they enter a wastewater disposal system. Common wastewater contains small amounts of oils which enter into septic tanks and treatment facilities to form a floating scum layer. This scum layer is very slowly digested and broken down by microorganisms in the anaerobic digestion process. Large amounts of oil from food preparation in restaurants can overwhelm a septic tank or treatment facility, causing the release of untreated sewage into the environment. High-viscosity fats and cooking grease such as lard solidify when cooled, and can combine with other disposed solids to block drain pipes.

<span class="mw-page-title-main">Drain (plumbing)</span> Vessel or conduit for unwanted water or waste liquids to be flumed away

A drain is the primary vessel or conduit for unwanted water or waste liquids to flow away, either to a more useful area, funnelled into a receptacle, or run into sewers or stormwater mains as waste discharge to be released or processed.

A Buchan trap is a device fitted in a domestic sewer pipe to prevent odours entering the pipe from the public sewer and permeating the house, a common problem before individual plumbing fittings were separately trapped. The trap is made from fireclay and uses a water seal to prevent air passing from the sewer to the pipe. Waste flows from the house through a U-bend in the trap. This means that there is always water in the pipe preventing the passage of anything from the other direction. The device is a large clay U-bend with an air-inlet/access point on the 'house' side. It is located below the ground level, but can be accessed through the air-inlet and sometimes a rodding hole.

<span class="mw-page-title-main">Toilet</span> Piece of hardware for the collection or disposal of human excreta

A toilet is a piece of sanitary hardware that collects human urine and feces, and sometimes toilet paper, usually for disposal. Flush toilets use water, while dry or non-flush toilets do not. They can be designed for a sitting position popular in Europe and North America with a toilet seat, with additional considerations for those with disabilities, or for a squatting posture more popular in Asia, known as a squat toilet. In urban areas, flush toilets are usually connected to a sewer system; in isolated areas, to a septic tank. The waste is known as blackwater and the combined effluent, including other sources, is sewage. Dry toilets are connected to a pit, removable container, composting chamber, or other storage and treatment device, including urine diversion with a urine-diverting toilet.

<span class="mw-page-title-main">Backflow</span> Unwanted reverse flow of water

Backflow is a term in plumbing for an unwanted flow of water in the reverse direction. It can be a serious health risk for the contamination of potable water supplies with foul water. In the most obvious case, a toilet flush cistern and its water supply must be isolated from the toilet bowl. For this reason, building codes mandate a series of measures and backflow prevention devices to prevent backflow.

References

  1. Deziel, Chris (18 Feb 2013). "How to Plumb for a Standpipe". Demand Media, San Francisco Chronicle . Retrieved 1 July 2016.
  2. 2010 Florida Building Code: Residential (PDF) (First printing, 2011, including January 2012 errata ed.). Country Club Hills, Illinois: International Code Council. January 2012. pp. 27.1–27.2. ISBN   978-1-60983-188-2 . Retrieved 1 July 2016.
  3. "Lute". Oxford Reference. Oxford University Press . Retrieved 21 December 2022.
  4. "50 Things That Made the Modern Economy: S-Bend". BBC. Retrieved 2018-11-02.
  5. Saltzman, Reuben (April 18, 2013). "How Bad Are Drum Traps?". The Home Inspector (blog). Star Tribune . Minneapolis. Archived from the original on July 15, 2015. Retrieved December 28, 2016. Includes several photographs of various types of drum traps.