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A swimming pool, swimming bath, wading pool, paddling pool, or simply pool, is a structure designed to hold water to enable
swimming Swimming is the self-propulsion of a person through water, or other liquid, usually for recreation, sport, exercise, or survival. Locomotion is achieved through coordinated movement of the limbs and the body to achieve hydrodynamic thrust whic ...
or other leisure activities. Pools can be built into the ground (in-ground pools) or built above ground (as a freestanding construction or as part of a building or other larger structure), and may be found as a feature aboard ocean-liners and cruise ships. In-ground pools are most commonly constructed from materials such as
concrete Concrete is a composite material A composite material (also called a composition material or shortened to composite, which is the common name) is a material Material is a substance Substance may refer to: * Substance (Jainism), a ter ...

concrete
, natural stone, metal, plastic, or
fiberglass Fiberglass (American English American English (AmE, AE, AmEng, USEng, en-US), sometimes called United States English or U.S. English, is the set of varieties of the English language native to the United States. Currently, American Englis ...
, and can be of a custom size and shape or built to a standardized size, the largest of which is the
Olympic-size swimming pool An Olympic-size swimming pool conforms to regulated dimensions that are large enough for international competition. This type of swimming pool swimming pool in Melbourne, Australia A swimming pool, swimming bath, wading pool, paddling poo ...
. Many
health club #REDIRECT Health club #REDIRECT Health club A health club (also known as a fitness club, fitness center, health spa, and commonly referred to as a gym) is a place that houses exercise equipment for the purpose of physical exercise. In recen ...
s,
fitness center #REDIRECT Health club #REDIRECT Health club #REDIRECT Health club A health club (also known as a fitness club, fitness center, health spa, and commonly referred to as a gym) is a place that houses exercise equipment for the purpose of physica ...
s, and private clubs have pools used mostly for exercise or recreation. It is common for municipalities of every size to provide pools for public use. Many of these municipal pools are outdoor pools but indoor pools can also be found in buildings such as leisure centers. Hotels may have pools available for their guests to use at their own leisure. Pools as a feature in hotels are more common in tourist areas or near
convention center A convention center (American English American English (AmE, AE, AmEng, USEng, en-US), sometimes called United States English or U.S. English, is the set of varieties of the English language native to the United States. Currently, A ...

convention center
s. Educational facilities such as high schools and universities sometimes have pools for physical education classes, recreational activities, leisure, and competitive athletics such as swimming teams.
Hot tub A hot tub is a large tub full of water used for hydrotherapy Hydrotherapy, formerly called hydropathy and also called water cure, is a part of alternative medicine Alternative medicine is any practice that aims to achieve the healing ...

Hot tub
s and
spa A spa is a location where mineral-rich spring water (and sometimes seawater) is used to give medicinal baths. Spa towns or spa resorts (including hot springs resorts) typically offer various health treatments, which are also known as baln ...

spa
s are pools filled with water that is heated and then used for relaxation or
hydrotherapy Hydrotherapy, formerly called hydropathy and also called water cure, is a part of alternative medicine Alternative medicine is any practice that aims to achieve the healing effects of medicine Medicine is the science Science (from ...
. Specially designed swimming pools are also used for
diving Diving usually refers to: * Diving (sport), the sport of jumping into deep water * Underwater diving, human activity underwater for recreational or occupational purposes Diving or Dive may also refer to: Sports * Dive (American football), a typ ...
, water sports, and
physical therapy Physical therapy (PT), also known as physiotherapy, is one of the allied health professions Allied health professions are health care Health care, health-care, or healthcare is the maintenance or improvement of health via the preventive h ...

physical therapy
, as well as for the training of
lifeguard A lifeguard is a rescuer who supervises the safety and rescue of swimmers, surfers, and other water sports participants such as in a swimming pool, water park, beach, spa, river and lake. Lifeguards are trained in swimming and CPR/AED first ai ...
s and
astronaut An astronaut (from the Greek "astron" (ἄστρον), meaning "star", and "nautes" (ναύτης), meaning "sailor") is a person trained, equipped, and deployed by a List of human spaceflight programs, human spaceflight program to serve as a ...

astronaut
s. Swimming pools most commonly use chlorinated water or salt water and may be heated or unheated.


History

The " Great Bath" at the site of
Mohenjo-Daro Mohenjo-daro (; sd, موئن جو دڙو'', ''meaning 'Mound of the Dead Men';
in modern-day Pakistan was most likely the first swimming pool, dug during the 3rd millennium BC. This pool is , is lined with bricks, and was covered with a tar-based sealant.
Ancient Greeks Ancient Greece ( el, Ἑλλάς, Hellás) was a civilization belonging to a period of History of Greece, Greek history from the Greek Dark Ages of the 12th–9th centuries BC to the end of Classical Antiquity, antiquity ( AD 600). This era was ...
and
Romans Roman or Romans usually refers to: *Rome , established_title = Founded , established_date = 753 BC , founder = King Romulus , image_map = Map of comune of Rome (metropolitan city of Capital Rome, region Lazio, ...
built artificial pools for athletic training in the
palaestra A palaestra ( or ; also (chiefly British) palestra; grc-gre, παλαίστρα) was any site of an ancient Greek Ancient Greek includes the forms of the Greek language Greek ( el, label=Modern Greek Modern Greek (, , or , '' ...
s, for nautical games and for military exercises. Roman emperors had private swimming pools in which fish were also kept, hence one of the
Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the Roman Republic, it became ...

Latin
words for a pool was ''piscina''. The first heated swimming pool was built by
Gaius Maecenas Gaius Cilnius Maecenas ( – 8 BC) was a friend and political advisor to Octavian Caesar Augustus (23 September 63 BC19 August AD 14) was the first Roman emperor, reigning from 27 BC until his death in AD 14. His status as the f ...
in his gardens on the
Esquiline Hill The Esquiline Hill (; la, Collis Esquilinus; it, Esquilino ) is one of the seven hills of Rome, Seven Hills of Rome. Its southernmost cusp is the ''Oppius'' (Oppian Hill). Etymology The origin of the name ''Esquiline'' is still under much ...
of
Rome , established_title = Founded , established_date = 753 BC , founder = King Romulus , image_map = Map of comune of Rome (metropolitan city of Capital Rome, region Lazio, Italy).svg , map_caption = The te ...

Rome
, likely sometime between 38 and 8 BC. Gaius Maecenas was a wealthy imperial advisor to
Augustus Caesar Augustus (23 September 63 BC19 August AD 14) was the first Roman emperor The Roman emperor was the ruler of the Roman Empire during the imperial period (starting in 27 BC). The emperors used a variety of different titles through ...

Augustus
and considered one of the first patrons of arts. Ancient
Sinhalese Sinhala may refer to: * Something of or related to the Sinhalese people of Sri Lanka * Sinhalese people * Sinhala language, one of the three official languages used in Sri Lanka * Sinhala script, a writing system for the Sinhala language ** Sinhala ...
built pairs of pools called " Kuttam Pokuna" in the kingdom of
Anuradhapura Anuradhapura ( si, අනුරාධපුරය, translit=Anurādhapuraya; ta, அனுராதபுரம், translit=Aṉurātapuram) is a major city in Sri Lanka Sri Lanka (, ; si, ශ්‍රී ලංකා, Śrī Laṅkā, t ...

Anuradhapura
,
Sri Lanka Sri Lanka (, ; si, ශ්‍රී ලංකාව, Śrī Laṅkā, translit-std=ISO (); ta, இலங்கை, Ilaṅkai, translit-std=ISO ()), formerly known as Ceylon, and officially the Democratic Socialist Republic of Sri Lanka, is ...

Sri Lanka
in the 4th century BC. They were decorated with flights of steps, punkalas or pots of abundance, and scroll design.


19th century

Swimming pools became popular in Britain in the mid-19th century. As early as 1837, six indoor pools with diving boards existed in London, England. The Maidstone Swimming Club in
Maidstone Maidstone is the largest town A town is a human settlement. Towns are generally larger than villages and smaller than city, cities, though the criteria to distinguish between them vary considerably in different parts of the world. Origi ...
,
Kent Kent is a county A county is a geographical region of a country used for administrative or other purposesChambers Dictionary The ''Chambers Dictionary'' (''TCD'') was first published by William Chambers (publisher), William and Robert ...

Kent
is believed to be the oldest surviving swimming club in Britain. It was formed in 1844, in response to concerns over drownings in the
River Medway The River Medway is a river in South East England South East England is one of the nine official regions of England at the ITL 1 statistical regions of England, first level of International Territorial Level, ITL for Statistics, statist ...
, especially since would-be rescuers would often drown because they themselves could not swim to safety. The club used to swim in the River Medway, and would hold races, diving competitions and
water polo Water polo is a competitive sport, competitive team sport played in water between two teams of seven players each. The game consists of four quarters in which the two teams attempt to score goals by throwing the water polo ball, ball into the ...
matches. ''The South East Gazette'' July 1844 reported an aquatic breakfast party: coffee and biscuits were served on a floating raft in the river. The coffee was kept hot over a fire; club members had to tread water and drink coffee at the same time. The last swimmers managed to overturn the raft, to the amusement of 150 spectators. The
Amateur Swimming Association Swim England is the national governing body for swimming, diving, water polo Water polo is a competitive sport, competitive team sport played in water between two teams of 7 players each. The game consists of four quarters in which the two te ...
was founded in 1869 in England, and the Oxford Swimming Club in 1909. The presence of indoor baths in the cobbled area of
Merton Street Merton Street is a historic and picturesque cobbled street in central Oxford, England.M ...

Merton Street
might have persuaded the less hardy of the aquatic brigade to join. So, bathers gradually became swimmers, and bathing pools became swimming pools. In 1939,
Oxford Oxford () is a city in England. It is the county town In the United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain,Usage is mixed. The Guardian' and Telegraph' u ...

Oxford
created its first major public indoor pool at Temple Cowley. The modern
Olympic Games The modern Olympic Games or Olympics (french: Jeux olympiques) are leading international sporting events featuring summer and winter sports competitions in which thousands of athletes An athlete (also sportsman or sportswoman) is a pe ...
started in 1896 and included swimming races, after which the popularity of swimming pools began to spread. In the US, the Racquet Club of Philadelphia clubhouse (1907) boasts one of the world's first modern above-ground swimming pools. The first swimming pool to go to sea on an ocean liner was installed on the
White Star Line The Oceanic Steam Navigation Company, more commonly known as the White Star Line (WSL), was a British shipping company. Founded out of the remains of a defunct packet company, it gradually rose up to become one of the most prominent shipping ...
's ''Adriatic'' in 1906. The oldest known public swimming pool in the U.S., Underwood Pool, is located in
Belmont, Massachusetts Belmont is a New England town, town in Middlesex County, Massachusetts. It is a western suburb of Boston, Boston, Massachusetts, United States; and is part of the greater Boston metropolitan area. Its population was 26,123 as of November 25, 2019. ...
. Interest in competitive swimming grew following
World War I World War I, often abbreviated as WWI or WW1, also known as the First World War or the Great War, was a global war A world war is "a war engaged in by all or most of the principal nations of the world". The term is usually reserved for ...

World War I
. Standards improved and training became essential. Home swimming pools became popular in the United States after
World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a global war A world war is "a war War is an intense armed conflict between states State may refer to: Arts, entertainment, and media Literatur ...
and the publicity given to swimming sports by Hollywood films such as
Esther Williams Esther Jane Williams (August 8, 1921 – June 6, 2013) was an American competitive swimmer and actress. She set regional and national records in her late teens on the Los Angeles Athletic Club swim team. Unable to compete in the 1940 Summer ...

Esther Williams
' ''
Million Dollar Mermaid ''Million Dollar Mermaid'' (also known as ''The One Piece Bathing Suit'' in the UK) is a 1952 Metro-Goldwyn-Mayer Metro-Goldwyn-Mayer Studios Inc. (also known as Metro-Goldwyn-Mayer Pictures, initialized as MGM; often referred to as Metro; ...
'' made a home pool a desirable status symbol. More than 50 years later, the home or residential swimming pool is a common sight. Some small nations enjoy a thriving swimming pool industry (e.g., New Zealand pop. 4,116,900 – holds the record in pools per capita with 65,000 home swimming pools and 125,000 spa pools). A two-storey, white concrete swimming pool building composed of horizontal cubic volumes built in 1959 at the
Royal Roads Military College Royal Roads Military College (RRMC) was a Canadian Military academy, military college from 1940 to 1995, located in Hatley Park, Colwood, British Columbia, near Victoria, British Columbia, Canada. The facility now serves as the campus of Royal Roa ...
is on the Registry of Historic Places of Canada.


World records

According to the
Guinness World Records ''Guinness World Records'', known from its inception in 1955 until 1999 as ''The Guinness Book of Records'' and in previous United States editions as ''The Guinness Book of World Records'', is a reference book A reference work is a work, ...
, the largest swimming pool in the world is
San Alfonso del Mar San Alfonso del Mar is a private resort in Algarrobo, Chile, about west of Santiago. The resort had one of the world's List of largest swimming pools, largest swimming pools. At the time of its completion in 2006, it was in the Guinness Book of Wo ...

San Alfonso del Mar
Seawater pool in Algarrobo,
Chile Chile, officially the Republic of Chile, is a country in the western part of South America South America is a entirely in the and mostly in the , with a relatively small portion in the . It can also be described as the southern ...

Chile
. It is long and has an area of 8 ha (20 acres). At its deepest, it is deep. It was completed in December 2006. The largest indoor
wave pool A wave pool is a swimming pool swimming pool in Melbourne, Australia A swimming pool, swimming bath, wading pool, paddling pool, or simply pool is a structure designed to hold water to enable Human swimming, swimming or other leisure activ ...
in the world is at
DreamWorks Water Park DreamWorks Water Park is an indoor water park within the American Dream The American Dream is a national ethos of the United States The United States of America (USA), commonly known as the United States (U.S. or US), or America, is ...
within the
American Dream The American Dream is a national ethos Ethos ( or ) is a Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located ...
shopping and entertainment complex at the
Meadowlands Sports Complex The Meadowlands Sports Complex is a sports complexA sports complex is a group of sports facilities. For example, there are track and field stadiums, football stadiums, baseball stadiums, swimming pools swimming pool in Melbourne M ...
in
East Rutherford, New Jersey East Rutherford is a borough A borough is an administrative division in various English language, English-speaking countries. In principle, the term ''borough'' designates a self-governing walled town, although in practice, official use of ...

East Rutherford, New Jersey
, United States, and the largest indoor pool in North America is at the
Neutral Buoyancy Lab The Neutral Buoyancy Laboratory (NBL) is an astronaut training facility and neutral buoyancy pool operated by NASA and located at the Sonny Carter Training Facility, near the Johnson Space Center in Houston, Texas. The NBL's main feature is a la ...
in the Sonny Carter Training Facility at
NASA The National Aeronautics and Space Administration (NASA; ) is an independent agency A regulatory agency or regulatory authority, is a Public benefit corporation Public-benefit corporation is a term that has different meanings in differen ...

NASA
JSC in Houston. In 2021, Deep Dive Dubai, located in Dubai, UAE, was certified by the
Guinness Book of World Records ''Guinness World Records'', known from its inception in 1955 until 1999 as ''The Guinness Book of Records'' and in previous United States editions as ''The Guinness Book of World Records'', is a reference book A reference work is a work, ...
as the world's deepest swimming pool. The Y-40 swimming pool at the Hotel Terme Millepini in
Padua Padua ( ; it, Padova ; vec, Pàdova) is a city and ''comune The (; plural: ) is a Administrative division, local administrative division of Italy, roughly equivalent to a township or municipality. Importance and function The pro ...
, Italy, previously held the record, , from 2014 until 2021. The Fleishhacker Pool in San Francisco was the largest heated outdoor swimming pool in the United States. Opened on 23 April 1925, it measured and was so large that the lifeguards required
kayak A kayak is a small, narrow watercraft Watercraft, also known as water vessels or waterborne vessels, are vehicles A vehicle (from la, vehiculum) is a machine A machine is any physical system with ordered structural and functional pr ...

kayak
s for patrol. It was closed in 1971 due to low patronage. In Europe, the largest swimming pool opened in 1934 in
Elbląg Elbląg (; german: Elbing; Old Prussian language, Old Prussian: ) is a city in northern Poland on the eastern edge of the Żuławy region with 119,317 inhabitants (December 2019). It is the capital of Elbląg County and has been assigned (since 1 ...
(
Poland Poland, officially the Republic of Poland, is a country located in Central Europe. It is divided into 16 Voivodeships of Poland, administrative provinces, covering an area of , and has a largely Temperate climate, temperate seasonal cli ...

Poland
), providing a water area of . One of the largest swimming pools ever built was reputedly created in
Moscow Moscow ( , American English, US chiefly ; rus, links=no, Москва, r=Moskva, p=mɐˈskva, a=Москва.ogg) is the Capital city, capital and List of cities and towns in Russia by population, largest city of Russia. The city stands on the ...

Moscow
after the
Palace of Soviets The Palace of the Soviets (russian: Дворец Советов, ''Dvorets Sovetov'') was a project to construct an administrative center and a congress hall in Moscow, Russian Soviet Federative Socialist Republic, Russian SFSR, Soviet Union (pres ...
remained uncompleted. The foundations of the palace were converted into the
Moskva Pool The Moskva Pool (Moscow Pool) was, for a time, the world's largest open air swimming pool A swimming pool, swimming bath, wading pool, paddling pool, or simply pool, is a structure designed to hold water to enable Human swimming, swimmin ...
open-air swimming pool after the process of de-Stalinisation. However, after the fall of
communism Communism (from Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the Roman Repu ...

communism
,
Christ the Saviour Cathedral
Christ the Saviour Cathedral
was re-built on the site between 1995 and 2000; the cathedral had originally been located there. The highest swimming pool is believed to be in Yangbajain (Tibet, China). This resort is located at 4200 m AMSL and has two indoor swimming pools and one outdoor swimming pool, all filled with water from
hot spring A hot spring, hydrothermal spring, or geothermal spring is a spring Spring(s) may refer to: Common uses * Spring (season), a season of the year * Spring (device), a mechanical device that stores energy * Spring (hydrology), a natural source of w ...

hot spring
s.


Dimensions

:''See: Competition pools (below)'' Length: Most pools in the world are measured in metres, but in the United States pools are often measured in feet and yards. In the UK most pools are calibrated in metres, but older pools measured in yards still exist. In the US, pools tend to either be 25 yards (SCY-
short course In Swimming (sport), swimming, the term short course (abbreviated SC) is used to identify a pool that is in length. The term is also often included in meet names when conducted in a short course pool. "Short course" is the second type of pool conf ...
yards), 25 metres (SCM-short course metres) or 50 metres (
long course An Olympic-size swimming pool conforms to regulated dimensions that are large enough for international competition. This type of swimming pool is used in the Olympic Games, where the race course is in length, typically referred to as "long cours ...
). US high schools and the
NCAA The National Collegiate Athletic Association (NCAA) is a nonprofit organization A nonprofit organization (NPO), also known as a non-business entity, not-for-profit organization, or nonprofit institution, is a legal entity organized and o ...
conduct short course (25 yards) competition. There are also many pools  m long, so that 3 lengths = 100 m. This pool dimension is commonly used to accommodate water polo.
USA Swimming USA Swimming is the national governing body for competitive swimming in the United States. It is charged with selecting the United States Olympic Swimming team and any other teams which officially represent the United States, as well as the over ...
(USA-S) swims in both metric and non-metric pools. However, the international standard is metres, and world records are only recognized when swum in 50 m pools (or 25 m for short course) but 25-yard pools are very common in the US. In general, the shorter the pool, the faster the time for the same distance, since the swimmer gains speed from pushing off the wall after each turn at the end of the pool. Width: Most European pools are between 10 m and 50 m wide. Depth: The depth of a swimming pool depends on the purpose of the pool, and whether it is open to the public or strictly for private use. If it is a private casual, relaxing pool, it may go from deep. If it is a public pool designed for diving, it may slope from in the deep end. A children's play pool may be from deep. Most public pools have differing depths to accommodate different swimmer requirements. In many jurisdictions, it is a requirement to show the water depth with clearly marked depths affixed to the pool walls.


Types

Pools can be either indoors or outdoors. They can be of any size and shape, and inground or above ground. Most pools are permanent fixtures, while others are temporary, collapsible structures.


Private pools

Private pools are usually smaller than public pools, on average to whereas public pools usually start at . Home pools can be permanently built-in, or be assembled above ground and disassembled after summer. Privately owned outdoor pools in backyards or gardens started to proliferate in the 1950s in regions with warm summer climates, particularly in the United States with
desegregation Desegregation is the process of ending the separation of two groups, usually referring to races. Desegregation is typically measured by the index of dissimilarity, allowing researchers to determine whether desegregation efforts are having impact o ...
. Construction methods for private pools vary greatly. The main types of in-ground pools are gunite
shotcrete Shotcrete, gunite (), or sprayed concrete is concrete Concrete is a composed of fine and coarse bonded together with a fluid (cement paste) that hardens (cures) over time. Concrete is the second-most-used substance in the world a ...
, concrete,
vinyl Vinyl may refer to: * Vinyl group In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, properties, behavior an ...
-lined, and one-piece fiberglass shells. Many countries now have strict pool fencing requirements for private swimming pools, which require pool areas to be isolated so that unauthorized children younger than six years cannot enter. Many countries require a similar level of protection for the children residing in or visiting the house, although many pool owners prefer the visual aspect of the pool in close proximity to their living areas, and will not provide this level of protection. There is no consensus between states or countries on the requirements to fence private swimming pools, and in many places they are not required at all, particularly in rural settings.


Children's pools

Inexpensive temporary
polyvinyl chloride Polyvinyl chloride (colloquial Colloquialism or colloquial language is the style (sociolinguistics), linguistic style used for casual (informal) communication. It is the most common functional style of speech, the idiom normally employed in ...
pools can be bought in supermarkets and taken down after summer. They are used mostly outdoors in yards, are typically shallow, and often their sides are inflated with air to stay rigid. When finished, the water and air can be let out and this type of pool can be folded up for convenient storage. They are regarded in the swimming pool industry as "splasher" pools intended for cooling off and amusing toddlers and children, not for swimming, hence the alternate name of "kiddie" pools.
Toy A toy is an item that is used primarily by children though may also be marketed to adults under certain circumstances. Playing with toys can be an enjoyable means of training young children for life experiences. Different materials like wood, ...

Toy
s are available for children and other people to play with in pool water. They are often blown up with air so they are soft but still reasonably rugged, and can float in water. File:Black Labrador Retriever kiddie pool..jpg, A bathing in a kiddie pool File:Kids.jpg, Children playing in an inflatable pool


Public pools

Public pools are often part of a larger leisure center or recreational complex. These centres often have more than one pool, such as an indoor heated pool, an outdoor (
chlorinated In chemistry, halogenation is a chemical reaction that involves the addition of one or more halogens to a chemical compound, compound or material. The pathway and stoichiometry of halogenation depends on the structural features and functional gro ...
,
saltwater Saline water (more commonly known as salt water) is water Water is an Inorganic compound, inorganic, Transparency and translucency, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the ...
or ozonated) pool which may be heated or unheated, a shallower children's pool, and a paddling pool for toddlers and infants. There may also be a
sauna A sauna (, ), or sudatory, is a small room or building designed as a place to experience dry or wet heat sessions, or an establishment with one or more of these facilities. The steam and high heat make the bathers perspire. A thermometer in a s ...

sauna
and one or more
hot tub A hot tub is a large tub full of water used for hydrotherapy Hydrotherapy, formerly called hydropathy and also called water cure, is a part of alternative medicine Alternative medicine is any practice that aims to achieve the healing ...

hot tub
s or
spa A spa is a location where mineral-rich spring water (and sometimes seawater) is used to give medicinal baths. Spa towns or spa resorts (including hot springs resorts) typically offer various health treatments, which are also known as baln ...

spa
pools ("
jacuzzi Jacuzzi Brands LLC (; ), through its subsidiaries, is a global manufacturer and distributor of branded bath Bath may refer to: * Bathing, immersion in a fluid ** Bathtub, a large open container for water, in which a person may wash their body ** ...

jacuzzi
s"). Many upscale hotels and holiday resorts have a swimming pool for use by their guests. If a pool is in a separate building, the building may be called a
natatorium A natatorium (plural: natatoriums or natatoria, also called swimming hall) is a building containing a swimming pool A swimming pool, swimming bath, wading pool, paddling pool, or simply pool, is a structure designed to hold water to enable ...
. The building may sometimes also have facilities for related activities, such as a diving tank. Larger pools sometimes have a
diving board
diving board
affixed at one edge above the water. Many public swimming pools are
rectangle In Euclidean geometry, Euclidean plane geometry, a rectangle is a quadrilateral with four right angles. It can also be defined as: an equiangular quadrilateral, since equiangular means that all of its angles are equal (360°/4 = 90°); or a para ...

rectangle
s 25 m or 50 m long, but they can be any size and shape. There are also elaborate pools with
artificial waterfall An artificial waterfall is a water feature or fountain A fountain (from the Latin "fons" (genitive "fontis"), a source or Spring (hydrology), spring) is a structure which squirts water into a basin to supply drinking water. It is also a struc ...

artificial waterfall
s, fountains,
splash pad A splash pad or spray pool is a recreation area, often in a public park, for water play (activity), play that has little or no standing water. This is said to eliminate the need for lifeguards or other supervision, as there is little risk of dr ...
s, wave machines, varying depths of water, bridges, and island bars. Some swimming facilities have
locker A locker is a small, usually narrow storage compartment. They are commonly found in dedicated cabinets, very often in large numbers, in various public places such as locker rooms A changing room, locker room, dressing room (usually in a s ...

locker
s for clothing and other belongings. The lockers can require a coin to be inserted in a slot, either as deposit or payment. There are usually showers – sometimes mandatory – before and/or after swimming. There are often also lifeguards to ensure the safety of users. Wading or paddling pools are shallow bodies of water intended for use by small children, usually in parks. Concrete wading pools come in many shapes, traditionally rectangle, square or circle. Some are filled and drained daily due to lack of a filter system. Staff chlorinate the water to ensure health and safety standards.


Competition pools

: ''See: #Dimensions (above) and Swimming (sport)#Competition pools'' The Fédération Internationale de la Natation (FINA, International Swimming Federation) sets standards for competition pools: long and at least deep. Competition pools are generally indoors and heated to enable their use all year round, and to more easily comply with the regulations regarding temperature, lighting, and automatic officiating equipment. An
Olympic-size swimming pool An Olympic-size swimming pool conforms to regulated dimensions that are large enough for international competition. This type of swimming pool swimming pool in Melbourne, Australia A swimming pool, swimming bath, wading pool, paddling poo ...
(first used at the 1924 Olympics) is a pool that meets FINA's additional standards for the Olympic Games and for world championship events. It must be wide, divided into eight lanes of each, plus two areas of at each side of the pool. Depth must be at least . The water must be kept at and the lighting level at greater than 1500
lux The lux (symbol: lx) is the SI derived unit SI derived units are units of measurement derived from the seven SI base unit, base units specified by the International System of Units (SI). They are either dimensionless quantity, dimensionless or ...

lux
. There are also regulations for color of lane rope, positioning of backstroke flags (5 metres from each wall), and so on. Pools claimed to be "Olympic pools" do not always meet these regulations, as FINA cannot police use of the term.
Touchpads A touchpad or trackpad is a pointing device featuring a tactile sensor, a specialized surface that can translate the motion and position of a user's fingers to a relative position on the operating system that is made output to the screen. Touchp ...
are mounted on both walls for long course meets and each end for short course. A pool may be referred to as fast or slow, depending on its physical layout. Some design considerations allow the reduction of swimming
resistance Resistance may refer to: Arts, entertainment, and media Comics * Either of two similarly named but otherwise unrelated comic book series, both published by Wildstorm: ** ''Resistance'' (comics), based on the video game of the same title ** ''Th ...
making the pool faster: namely, proper pool depth, elimination of currents, increased lane width, energy absorbing racing lane lines and gutters, and the use of other innovative hydraulic, acoustic and illumination designs.


Exercise pools

In the last two decades, a new style of pool has gained popularity. These consist of a small vessel (usually about 2.5 × 5 m) in which the swimmer swims in place, either against the push of an artificially generated water current or against the pull of restraining devices. These pools have several names, such as ''swim spas'', ''
swimming machine A swimming machine is a resistance swimming apparatus, often self-contained, enabling the swimmer to swim in place. This may be accomplished either by accelerating the water past the swimmer or by supporting the swimmer, either in water or on dr ...
s'', or ''swim systems''. They are all examples of different modes of
resistance swimming Resistance swimming is a form of swimming Swimming is the self-propulsion of a person through water Water is an Inorganic compound, inorganic, Transparency and translucency, transparent, tasteless, odorless, and Color of water, nearly ...
.


Hot tubs and spa pools

Hot tubs and spa pools are common heated pools used for relaxation and sometimes for therapy. Commercial spas are common in the swimming pool area or sauna area of a
health club #REDIRECT Health club #REDIRECT Health club A health club (also known as a fitness club, fitness center, health spa, and commonly referred to as a gym) is a place that houses exercise equipment for the purpose of physical exercise. In recen ...
or fitness center, in men's clubs, women's clubs, motels and exclusive five-star hotel suites. Spa clubs may have very large pools, some segmented into increasing temperatures. In Japan, men's clubs with many spas of different size and temperature are common. Commercial spas are generally made of concrete, with a mosaic tiled interior. More recently with the innovation of the pre-form composite method where mosaic tiles are bonded to the shell this enables commercial spas to be completely factory manufactured to specification and delivered in one piece. Hot tubs are typically made somewhat like a wine barrel with straight sides, from wood such as Californian redwood held in place by metal hoops. Immersion of the head is not recommended in spas or hot tubs due to a potential risk of underwater entrapment from the pump suction forces. However, commercial installations in many countries must comply with various safety standards which reduce this risk considerably. Home spas are a worldwide retail item in western countries since the 1980s, and are sold in dedicated spa stores, pool shops, department stores, the Internet, and catalog sales books. They are almost always made from heat-extruded Polymethyl methacrylate, acrylic sheet Perspex, often colored in marble look-alike patterns. They rarely exceed and are typically deep, restricted by the availability of the raw sheet sizes (typically manufactured in Japan). There is often a mid-depth seating or lounging system, and contoured lounger style reclining seats are common. Upmarket spas include various jet nozzles (massage, pulsating, etc.), a drinks tray, lights, LCD flat-screen TV sets and other features that make the pool a recreation center. Due to their family-oriented nature, home spas are normally operated from . Many pools are incorporated in a Coast Redwood, redwood or simulated wood surround, and are termed "portable" as they may be placed on a patio rather than sunken into a permanent location. Some portable spas are shallow and narrow enough to fit sideways through a standard door and be used inside a room. Low power electric immersion heaters are common with home spas. Whirlpool tubs first became popular in the U.S. during the 1960s and 1970s. A spa is also called a "jacuzzi" there, as the word became a generic after-plumbing component manufacturer; Jacuzzi introduced the "spa whirlpool" in 1968. Air bubbles may be introduced into the nozzles via an air-bleed venturi pump that combines cooler air with the incoming heated water to cool the pool if the temperature rises uncomfortably high. Some spas have a constant stream of bubbles fed via the seating area of the pool, or a footwell area. This is more common as a temperature control device where the heated water comes from a natural (uncontrolled heat) geothermal source, rather than artificially heated. Water temperature is usually very warm to hot – – so bathers usually stay in for only 20 to 30 minutes. Bromine or mineral sanitizers are often recommended as sanitizers for spas because chlorine dissipates at a high temperature, thereby heightening its strong chemical smell. Ozone is an effective bactericide and is commonly included in the circulation system with cartridge filtration, but not with sand media filtration due to clogging problems with turbid body fats.


Ocean pools

In the early 20th century, especially in Australia, Ocean pools in Australia, ocean pools were built, typically on headlands by enclosing part of the rock shelf, with water circulated through the pools by flooding from tidal tanks or by regular flooding over the side of the pools at high tide. This continued a pre-European tradition of bathing in rockpools with many of the current sites being expanded from sites used by Aboriginal Australians or early European settlers. Bathing in these pools provided security against both rough surf and sea life. There were often separate pools for women and men, or the pool was open to the sexes at different times with a break for bathers to climb in without fear of observation by the other sex. These were the forerunners of modern "Olympic" pools. A variation was the later development of sea- or harbour-side pools that circulated sea water using pumps. A pool of this type was the training ground for Australian Olympian Dawn Fraser. There are currently about 100 ocean baths in New South Wales, which can range from small pools roughly 25 metres long and "Olympic Sized" (50m) to the very large, such as the 50 × 100 m baths in Newcastle, New South Wales, Newcastle. While most are free, a number charge fees, such as the Bondi Icebergs Club pool at Bondi Beach. Despite the development of chlorinated and heated pools, ocean baths remain a popular form of recreation in New South Wales. A semi-natural ocean pool exists on the central coast of New South Wales; it is called The Bogey Hole.


Infinity pools

An infinity pool (also named ''negative edge'' or ''vanishing edge pool'') is a swimming pool which produces a visual effect of water extending to the horizon, vanishing, or extending to "infinity". Often, the water appears to fall into an ocean, lake, bay, or other similar body of water. The illusion is most effective whenever there is a significant change in elevation, though having a natural body of water on the horizon is not a limiting factor.


Natural pools and ponds

Natural pools were developed in central and western Europe in the early and mid-1980s by designers and landscape architects with environmental concerns. They have recently been growing in popularity as an alternative to traditional swimming pools. Natural pools are constructed bodies of water in which no chemicals or devices that disinfect or sterilize water are used, and all the cleaning of the pool is achieved purely with the motion of the water through biological filters and plants rooted hydroponically in the system. In essence, natural pools seek to recreate swimming holes and swimmable lakes, the environment where people feel safe swimming in a non-polluted, healthy, and ecologically balanced body of water. Water in natural pools has many desirable characteristics. For example, red eyes, dried-out skin and hair, and bleached bathing suits associated with overly chlorinated water are naturally absent in natural pools. Natural pools, by requiring a water garden to be a part of the system, offer different aesthetic options and can support amphibious wildlife such as snails, frogs, and salamanders, and even small fish if desired.


Zero-entry swimming pools

A ''zero-entry swimming pool'', also called a ''beach entry swimming pool'', has an edge or entry that gradually slopes from the deck into the water, becoming deeper with each step, in the manner of a natural beach. As there are no stairs or ladders to navigate, this type of entry assists older people, young children and people with Disability, accessibility problems (e.g., people with a physical disability) where gradual entry is useful.


Indoor pools

Indoor pools are located inside, under a roof and insulated by at least three walls. Built for the purpose of year-round swimming or training, they are found in all climate types. Since the pool room is insulated, it is less likely the heat will escape; making it less expensive to heat than an outdoor pool where the heat will escape. Architecturally, the indoor pool may look like the rest of the house, but in terms of engineering, variables such as heating and ventilation are required to ensure comfortable humidity levels. In addition to drainage and automatic pool covers, there are a number of ways to remove humidity in the air that is present with any wet indoor environment. Efficient Dehumidifier, dehumidification in the indoor pool environment prevents structural damage, lowers energy costs for cooling or heating in addition to improving the room's climate to make it a comfortable swimming environment.


Other uses

Swimming pools are also used for events such as synchronised swimming, synchronized swimming,
water polo Water polo is a competitive sport, competitive team sport played in water between two teams of seven players each. The game consists of four quarters in which the two teams attempt to score goals by throwing the water polo ball, ball into the ...
, canoe polo and underwater sports such as underwater hockey, underwater rugby, finswimming and sport diving (sport), sport diving as well as for teaching
diving Diving usually refers to: * Diving (sport), the sport of jumping into deep water * Underwater diving, human activity underwater for recreational or occupational purposes Diving or Dive may also refer to: Sports * Dive (American football), a typ ...
, Lifeguards, lifesaving and scuba diving techniques. They have also been used for specialist tasks such as teaching water-ditching survival techniques for aircraft and submarine crews and
astronaut An astronaut (from the Greek "astron" (ἄστρον), meaning "star", and "nautes" (ναύτης), meaning "sailor") is a person trained, equipped, and deployed by a List of human spaceflight programs, human spaceflight program to serve as a ...

astronaut
training. Round-cornered, irregular swimming pools, such as the Nude Bowl, were drained of water and used for vertical skateboarding.


Sanitation

Levels of bacteria and viruses in swimming pool water must be kept low to prevent the spread of diseases and pathogens. Bacteria, algae and insect larvae can enter the pool if water is not properly sanitized. Pumps, mechanical sand filters, and disinfectants are often used to sanitise the water. Chemical disinfectants, such as chlorine (usually as a hypochlorite salt, such as calcium hypochlorite) and bromine, are commonly used to kill pathogens. If not properly maintained, chemical sanitation can produce high levels of disinfection byproducts. Sanitized swimming pool water can theoretically appear green if a certain amount of iron salts or copper chloride are present in the water. Acesulfame potassium has been used to estimate how much urine is discharged by swimmers into a pool. In a Canadian study it was estimated that swimmers had released 75 litres of urine into a large pool that had about 830,000 litres of water and was a third of the size of an olympic pool.
Hot tub A hot tub is a large tub full of water used for hydrotherapy Hydrotherapy, formerly called hydropathy and also called water cure, is a part of alternative medicine Alternative medicine is any practice that aims to achieve the healing ...

Hot tub
s were found to have higher readings of the marker. While urine itself is sterile, its degradation products may lead to asthma.


Covers

Swimming pool heating costs can be significantly reduced by using a pool cover. Use of a pool cover also can help reduce the amount of chemicals (chlorine, etc.) required by the pool. Outdoor pools gain heat from the sun, absorbing 75–85% of the solar energy striking the pool surface. Though a cover decreases the total amount of solar heat absorbed by the pool, the cover eliminates heat loss due to evaporation and reduces heat loss at night through its insulating properties. Most swimming pool heat loss is through evaporation. The heating effectiveness of a cover depends on type. A transparent bubble cover is the most effective, as it allows the largest amount of solar flux into the pool itself. Thermal bubble covers are lightweight Ultraviolet, UV-stabilized floating covers designed to minimize heat loss on heated swimming pools. Typically they are only fitted in spring and fall (autumn) when the temperature difference between pool water and air temperature is greatest. When used consistently they can raise average pool temperatures of an outdoor pool by around 18 °Fahrenheit (11 °Celsius) when combined with a well sized solar pool heating system, or about 11° Fahrenheit (6 °Celsius) without a solar heater but with full sun exposure. Bubble covers are typically applied and removed by being rolled up on a device fitted to one side of the pool (see illustration). Covers fall apart after four or five years due to sun exposure, overheating in the sun while off the pool, and chlorine attacking the plastic. Bubble covers should be removed during superchlorination. A vinyl cover absorbs more sunlight directly, allowing temperature to rise faster, but ultimately prevents the pool from reaching as high a temperature as a clear cover. Vinyl covers consist of a heavier material and have a longer life expectancy than bubble covers. Insulated vinyl covers are also available with a thin layer of flexible insulation sandwiched between two layers of vinyl. These covers are mandatory to be fitted to all pools in areas of Australia that have experienced drought since 2006. This is an effort to conserve water, as much water evaporates and transpires. An alternative to a continuous sheet of pool covering is multiple floating disks which are deployed and removed disk by disk. They cover most of the surface of the pool and offer evaporation reduction similar to continuous covers. Various types are available, for example opaque (for UV resistance and possible reduced algal growth), transparent (for esthetics), heavy and solid (for wind resistance), light and inflatable (for ease of handling). ; Liquid covers Liquid covers are also an option. They use a microscopically thin layer of liquid (such as cetyl alcohol) that sits on the water surface and reduces evaporation, which is one of the major sources of heat loss as well as water loss. Unlike other covers, the pool can be used while the liquid cover is in place, and the nontoxic material is safe for people as well as pumping/filtering systems. The liquid must be replenished regularly (monthly or more), and may not be effective in windy areas (since the wind will disperse the thin layer). ; Safety covers These covers are typically attached all winter, by hooked bungee cords or hooked springs connected to the pool deck, and are usually made in a variety of materials including coated or laminated vinyl or polypropylene mesh. They are custom designed to stop leaf debris from entering the pool but more importantly they also provide safety for animals and small children when designed and installed properly. The custom safety cover was invented in 1957 by Fred Meyer Jr. of Meyco Pool Covers when he found a dead animal in his pool. Today covers are made to meet ASTM International, ASTM safety barrier standards and have kept animals, people and even large vehicles out of the pool. They are not popular in warmer climates, due to the five to ten minutes it takes to fit/remove them, making them inconvenient for repeated application and removal.


Pool cover automation

A pool cover can be either manually, semi-automatically, or automatically operated. Manual covers can be folded and stored in an off site location. Pool cover reels can also be used to help manually roll up the pool cover. The reel, usually on wheels, can be rolled in or out of place. Semi-automatic covers use a motor-driven reel system. They use electrical power to roll and unroll the cover, but usually require someone to pull on the cover when unrolling, or guide the cover onto the reel when rolling up the cover. Semi-automatic covers can be built into the pool deck surrounding the pool, or can use reels on carts. Automatic covers have permanently mounted reels that automatically cover and uncover the pool at the push of a button. They are the most expensive option, but are also the most convenient. These reels can be run from either an external motor requiring a pit to be dug beside the pool or using an internal motor that spins the reel. Some pool covers fit into tracks along the sides of the pool. This prevents anything or anybody from getting into the pool. They even support the weight of several people. They can be run manually, semi-automatically, or automatically. Safety covers may be required by inspectors for public pools.


Winterization

In areas which reach freezing temperature, it is important to close a pool properly. This varies greatly between in-ground and above-ground pools. By taking steps to properly secure the pool, it lessens the likelihood that the superstructure will be damaged or compromised by freezing water.


Closing vinyl and fibreglass pools

In preparation for freezing temperatures, an in-ground swimming pool's pipes must be emptied. An above-ground pool should also be closed, so that ice does not drag down the pool wall, collapsing its structure. The plumbing is sealed with air, typically with rubber plugs, to prevent cracking from freezing water. The pool is typically covered to prevent leaves and other debris from falling in. The cover is attached to the pool typically using a stretch cord, similar to a bungee cord, and hooks fitted into the pool surround. The skimmer is closed off or a floating device is placed into it to prevent it from completely freezing and cracking. Floating objects such as life rings or basketballs can be placed in the pool to avoid its freezing under the cover. Sand or DE filters must be backwashed, with the main drain plug removed and all water drained out. Drain plugs on the Filter (water), pool filter are removed after the filter has been cleaned. The pool pump motor is taken under cover. Winter chemicals are added to keep the pool clean. The innovation of a composite construction of fiberglass, with an epoxy coating and porcelain ceramic tiles has led to the pre-form, composite-type with significant advantages over older methods; however, it also has increased sensitivity to metal staining. In climates where there is no risk of freezing, closing down the pool for winter is not so important. Typically, the thermal cover is removed and stored. Winter sunlight can create an algae mess when a cover that has been left on all winter is removed. The pool is correctly pH-balanced and super-chlorinated. One part algaecide for every 50,000 parts of pool water should be added, and topped up each month. The pool should be filtered for one to two hours daily to keep the automated chlorination system active.


Safety

Pools pose a risk of drowning, which may be significant for swimmers who are inexperienced, suffer from seizures, or are susceptible to a heart or respiratory condition. Lifeguards are employed at most pools to execute water rescues and administer first aid as needed in order to reduce this risk. Diving in shallow areas of a pool may also lead to significant head and neck injuries; diving, especially head-first diving, should be done in the deepest point of the pool, minimally , but desirably , deeper if the distance between the water and the board is great. Pools also present a risk of death due to drowning, particularly in young children. In regions where residential pools are common, drowning is a major cause of childhood death. As a precaution, many jurisdictions require that residential pools be enclosed with Pool fence, fencing to restrict unauthorized access. Many products exist, such as removable baby fences. The evidence for floating alarms and window/door alarms to reduce the risk of drowning is poor. Some pools are equipped with computer-aided pool safety camera, drowning prevention or other forms of electronic safety and security systems. Suspended ceilings in indoor swimming pools are safety-relevant components. The selection of materials under tension should be done with care. Especially the selection of unsuitable stainless steels can cause problems with stress corrosion cracking.


Dress code

In public swimming pools, dress code may be stricter than on public beaches, and in indoor pools stricter than outdoor pools. For example, in countries where women can be topless on the beach, this is often not allowed in a swimming pool, and a swimsuit must be worn. For men, wearing ordinary shorts and a T-shirt to go in the water at a beach may be considered acceptable, but pools usually require real swim suits or other dedicated water wear. Swimming with regular clothes can potentially weigh a swimmer down should they need to be rescued. In France and some other European countries, board shorts are usually not allowed for "hygienic" reasons. In Nordic countries, in particular Iceland, rules about clothing and hygiene are especially strict. When diving from a high board, swimsuits are sometimes worn doubled up (one brief inside another) in case the outer suit tears on impact with the water.


See also

* Automated pool cleaner * Bather load * Lido * List of water games * Neutral buoyancy pool * Pool fence * Pool noodle * Respiratory risks of indoor swimming pools * Swimming pool service technician * Uniform Swimming Pool, Spa and Hot Tub Code * Urine-indicator dye


References


External links

* {{Authority control Swimming pools, Bodies of water Garden features Sports venues by type