Swimming pool

For the 2003 film, see Swimming Pool (film).

Backyard swimming pool

A swimming pool, swimming bath, wading pool, or simply a pool, is an artificially enclosed body of water intended for swimming or water-based recreation. There are many standard sizes; the largest and deepest is the Olympic size. A pool can be built either above or in the ground, and from materials such as metal, plastic or concrete.

Pools that may be used by many people or by the general public are called public, while pools used exclusively by a few people or in a home are called private. Many health clubs, fitness centers and private clubs have public pools used mostly for exercise. Many hotels and massage parlors have public pools for relaxation. Hot tubs and spas are pools with hot water, used for relaxation or therapy, and are common in homes, hotels, clubs and massage parlors. Swimming pools are also used for diving, other sports, and training of lifeguards and astronauts.

Pools must be sanitized to prevent growth and spread of bacteria, viruses, algae and insect larvae that can cause disease. This is done using filters and chemical disinfectants such as chlorine, bromine or mineral sanitizers.

History

The "great bath" at the site of Mohenjo-Daro was most likely dug during the 3rd millennium BC. This pool is 12 by 7 meters, is lined with bricks and was covered with a tar-based sealant.

Ancient Greeks and Romans built artificial pools for athletic training in the palaestras, for nautical games and for military exercises. Roman emperors had private swimming pools in which fish were also kept, hence the Latin word for pool, piscina. The first heated swimming pool was built by Gaius Maecenas of Rome in the first century BC. Gaius Maecenas was a rich Roman lord and considered one of the first patrons of arts.

Ancient Sinhalese built pairs of pools called "Kuttam Pokuna" in the kingdom of Anuradhapura, Sri Lanka in 4th century BC. Those were decorated with flights of steps, punkalas or pots of abundance and scroll design.

Swimming pools became popular in Britain in mid 19th century. By 1837, six indoor pools with diving boards were built in London, England. After the modern Olympic Games began in 1896 and included swimming races, the popularity of swimming pools began to spread (reference: Encyclopedia Britannica). In 1939, Oxford had its first major public indoor pool at Temple Cowley, and swimming began to take off. The Amateur Swimming Association was founded in 1869 in England, and the Oxford Swimming Club in 1909 with its home at Temple Cowley Pool. The presence of indoor baths in the cobbled area of Merton Street, London may have persuaded the less hardy of the aquatic brigade to join. So, bathers gradually became swimmers, and bathing pools swimming pools.

Deep Eddy Pool, built in 1915, is the oldest concrete swimming pool in Texas

In the USA, 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's Adriatic in 1907.

After World War I and the departure of "Long John" style swimming costumes, interest in competitive swimming grew. Standards improved and training became essential.

Home swimming pools became popular in the USA after World War II and the publicity given to swimming sports by Hollywood films like Esther Williams Million Dollar Mermaid made a home pool a desirable status symbol. More than 50 years later, the home or residential swimming pool is ubiquitous and even the smallest world nations enjoy a thriving swimming pool industry (e.g. New Zealand pop. 4,116,900 [Source NZ Census 7 March 2006] - holds the record in pools per capita with 65,000 home swimming pools and 125,000 spa pools).

World's largest

One of the largest swimming pools ever built was reputedly in Moscow after the Palace of Soviets remained uncompleted. The foundations were converted into an open air swimming pool after the process of de-Stalinisation. After the fall of communism, Christ the Saviour Cathedral was re-built (it had originally been on the site) between 1995 and 2000.

According to the Guinness World Records, the largest swimming pool in the world is San Alfonso del Mar Seawater pool in Algarrobo, Chile. It is 1,013 m (3,324 ft) long and has an area of 8 ha (20 acres). It was completed in December 2006.

The largest indoor wave pool in North America is at the West Edmonton Mall and the largest indoor pool is at the Neutral Buoyancy Lab in the Sonny Carter Training Center at NASA JSC in Houston. The recreational diving center Nemo 33 near Brussels, Belgium is home to the world's deepest swimming pool. The pool has two large flat-bottomed areas at depth levels of 5 m (16 ft) and 10 m (32 ft), and a large circular pit descending to a depth of 33 m (108 ft).

The Fleishhacker Pool in San Francisco, California was the largest swimming pool in the United States. Opened on 23 April 1925, it measured 300 m by 45 m (1,000 ft by 150 ft) and was so large that the lifeguards required kayaks for patrol. It was closed in 1971 due to low patronage.

Dimensions

Length

Most pools in the world are measured in metres, but in the United States pools are almost always measured in feet and yards. In the United Kingdom most pools are in metres, but older pools measured in yards still exist. In the US pools tend to either be 25 yards (SCY-short course yards), 25 metres (SCM-short course metres) or 50 metres (long course). US high schools and the NCAA conduct short course (25 yards) competition. There also exist many pools 33⅓ m long, so that 3 lengths = 100 m. This is sometimes jokingly referred to as "inter-course".

USA Swimming (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).

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.

Depth

A boy in a shallow children's pool.

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 1.0 m to 1.8 m (3 to 6 feet) deep. If it is a public pool designed for diving, it may slope from 3 to 4.8 m (10 to 14 feet) in the deep end. A children's play pool may be from 30 cm to 1.2 m (1 to 4 feet) 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.

After an incident in Washington state in 1993, most US and other pool builders are reluctant to equip a residential swimming pool with a diving springboard, so home diving pools are much less common these days. In the incident 14-year-old Shawn Meneely made a "suicide dive" in a private swimming pool and was seriously injured (tetraplegic). Family lawyer Fred Zeder successfully sued the diving board manufacturer, the pool builder, and the National Spa & Pool Institute over the inappropriate depth of the pool. The NSPI had specified a minimum depth of 8 ft 6 in (2.55m) which proved to be insufficient in the above case. The multi-million dollar lawsuit was eventually settled in 2001 for $US6,600,000 ($US8,000,000 after interest was added) in favor of the plaintiff. The NSPI was held to be liable, and was financially strained by the case. It filed twice for Chapter 11 bankruptcy protection and was successfully reorganized into a new swimming pool industry association.

Types

Ocean pools

An Ocean pool in Sydney, Australia

In the early 20th century, especially 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. 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 come without fear of observation by the other sex. Segregated changing sheds and showers were provided. These were the fore-runners of modern 'Olympic' pools. A variation was the later development of sea- or harbour-side pools that circulated sea water using pumps. The pool of this type at Balmain was the training ground for Olympian, Dawn Fraser.

Private pools

A Private Swimming pool

Rooftop pool in Manhattan.

A small inflatable "splasher" pool

Private pools are usually smaller than public pools, on average 16' x 32' (4.8m x 9.6 m) to 20' x 40' (6m x 12 m) whereas public pools usually start at 80 0" (25.0m). 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. In some warm-weather US locations, such as Florida and Arizona, home pools are so common that it is rare to find a new house being built without a pool being considered in the design.

Private pools are increasingly a feature of homes in greater latitudes. For example, in London many larger homes are now refurbished with indoor pools, usually in the basement or in a conservatory. In some European cities, including Munich, it is relatively common for people living in older properties to convert existing internal motorcar garages into indoor pool areas.

Construction methods for private pools vary greatly. The main types of in-ground pools are concrete, vinyl liner, and fiberglass. Above-ground pools (also called "on-ground pools") are usually cheaper to build. They are especially popular in places where ground freezing makes excavation difficult and threatens damage to the pool structure.

Inexpensive temporary PVC 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 that 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.

Some people use hot tubs and spas at home to soak their bodies in water for recreation.

Many toys 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.

Many countries now have strict pool fencing laws 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 general 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.

Public pools

Fun with inner tubes in a swimming pool.

Swimming pool of a resort in Curaçao.

Public pools are often found as part of a larger leisure centre or recreational complex. These centres often have more than one pool, such as an indoor heated pool, an outdoor saltwater or unheated chlorinated pool, a shallower children's pool, and a paddling pool for toddlers and infants. There may also be a sauna and one or more hot tubs or spa pools ("jacuzzis").

Public pools may belong to a hotel or holiday resort, as an amenity for the recreation of their guests. If a pool is located in a separate building, the building is called a "natatorium". The building sometimes also has facilities for related activities, such as a diving tank. Outdoor pools are common in warmer climates. Larger pools sometimes have a diving board affixed at one edge above the water. Diving pools should be deep enough that divers are not injured.

Many public swimming pools are rectangles 25 m or 50 m long, but may be any size and shape desired. There are also elaborate pools with artificial waterfalls, fountains, splash pads, wave machines, varying depths of water, bridges, and island bars.

There are often lockers for clothing and other belongings. The lockers often require a coin to be inserted as deposit or payment. There are often showers ready for use - sometimes mandatory - before or after swimming.

Wading 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. They are filled and drained daily due to lack of a filter system. Staff chlorinate the water to ensure health and safety standards.

Competition pools

The starting block of a competition swimming pool; they were first used at the 1936 Summer Olympics.

Federation Internationale de la Natation (International Swimming Federation) sets widely recognized standards for competition pools: 25 m (~82 feet) or 50 m (~164 feet) long and at least 1.35 m (~4.4 feet) 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 and equipment.

An Olympic sized swimming pool (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 50 m (~164 feet) in length by 25 m (~82 feet) wide, divided into eight lanes of 2.5 m (~8.2 feet) each plus two areas of 2.5 m (~8.2 feet) at each side of the pool. The water must be kept at 25–28°C (77-82.4°F) and the lighting level at greater than 1500 lux. Depth must be at least 2 m (~6.5 feet), and there are also regulations for color of lane rope, positioning of backstroke flags (5 meters 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 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 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 m x 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 machines, or swim systems. They are all examples of different modes of resistance swimming.

Hot tubs and spa pools

Indoor swimming pool with mineral water, Carolus Thermen, Aachen, Germany

Hot tubs, spa pools are common heated pools used for relaxation and sometimes for therapy. The "hippie" era (1950 - 1970) popularized them in America in songs and movies. A spa is also called a "jacuzzi" in USA since 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 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 — 38°C to 42°C (100 to 104 °F). So bathers usually spend a short time inside, 20 to 30 minutes at 39°C. 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.

Commercial spas are common in the swimming pool area or sauna area of a health club or fitness centre, in men's clubs, women's clubs, massage parlours, brothels, 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. 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. Total immersion (especially the head) is not recommended in commercial spas due to unknown health risks posed by the large number of bathers and their unknown activities.

Home spas are a world-wide 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 acrylic sheet Perspex, often colored in marble look-alike patterns. They rarely exceed 8 ft² (2,400mm²) and are typically 3 ft 6 in (1 m) 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 36°C to 39°C. Many pools are incorporated in a 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.

Infinity pools

Main article: Infinity pool

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 effect is best captured in a pool where the liner is painted to match the body of water it is "falling" into.

Other uses

An astronaut prepares to descend into a swimming pool

Swimming pools are also used for events such as synchronized swimming and water polo as well as for teaching diving and lifesaving techniques. They have also been used for specialist tasks such as teaching water-ditching survival techniques for helicopter crews and astronaut training. Round-cornered, irregular swimming pools, drained of water, were the first surfaces used for vertical skateboarding.

Sanitation

Main article: Swimming pool sanitation

Swimming pool water must be maintained at low levels of bacteria and viruses to prevent the spread of diseases and pathogens between users. Bacteria, algae and insect larvae can also enter the pool without help from swimmers, and cause disease to swimmers and other people in the area.

Pumps and mechanical filters are often used to filter such pathogens out of the water. Chemical disinfectants, such as hypochlorous acid, sodium hypochlorite (household bleach), bromine or mineral sanitizers, are used to make the water inhospitable to pathogens.

The wave of recent mortgage foreclosures in the United States has resulted in many people walking away from their homes without emptying their swimming pools. This resulted in the pools turning green with algae and becoming mosquito breeding grounds in less than a week.

Winterization

In areas which reach freezing temperature, it is important to close a pool properly. This varies greatly between inground and aboveground 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

A rolled up Thermal Bubble pool cover, used to reduce water loss from evaporation and heat loss from the pool.

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. Drain plugs on the 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.

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 litre algaecide for every 50,000 litres 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.

Covers

Swimming pool heating costs can be significantly reduced by using a pool cover. Use of a pool cover also can help reduce the size of a solar pool heating system, which can save money. Outdoor pools gain heat from the sun, absorbing 75%–85% of the solar energy striking the pool surface. This is an important contribution to the pool's heating needs. A pool cover will decrease the solar gain contribution to some extent, depending on what type you use. A transparent bubble cover may reduce pool solar energy absorption by 5%–15 %. A completely opaque cover will reduce it by 20%–40%.

Pool cover automation

Automatic Pool Cover

A pool cover can be either manually, semi-automatically, or automatically operated. Manual covers can be folded and stored in a convenient location. Pool cover reels can also be used to help manually roll up the pool cover. The reel, usually on wheels, can be rolled out of the way.

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.

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.

Pool cover materials

There are three main materials used for pool covers: Vinyl, thermal bubble and debris.

Vinyl covers

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.

Thermal bubble covers

Thermal bubble covers are lightweight 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. They raise temperature of a pool by around 20 °Fahrenheit after being on the pool for a week. Most heat in a pool is lost through evaporation.

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 4 or 5 years due to sun exposure, overheating in the sun while off the pool, and chlorine attacking the plastic.

Bubble covers should be removed during super chlorination.

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.

Debris covers

These covers are typically attached all winter, by hooked bungee cords or hooked springs connected to the pool deck, and are usually made of black or green fine PVC mesh. They are designed to stop leaf debris from entering the pool. They also provide some safety for animals and small children, but should not be relied on. They are not popular in warmer climates, due to the five to ten minutes it takes to fit/remove, making them inconvenient for repeated application and removal.

Safety

Trained Instructors teach children how to swim

Pools present a significant risk of infant and toddler death due to drowning. In regions where residential pools are common, drowning is a major cause of childhood fatalities. So it is advisable to closely watch small children around swimming pools, especially private pools that do not have professional lifeguards. Adults are more likely to be aware of risks, but it is still a good idea to have more than one person around when using a private pool. As a precaution, many municipalities have bylaws that require that residential pools be enclosed with fencing to restrict unauthorized access.

In public pools there is a lower risk of accident, with trained lifeguards on duty whenever the pool is open. Because of the risk of drowning and the desire for greater safety, and technological advances that make such safety possible, more and more public pools are equipped with computer-aided drowning prevention or other forms of electronic and sometimes automated safety and security systems. Among these are the Poseidon system, Swimguard, and the Drowning Early Warning System (DEWS).

The best way to ensure safety around pools is to be educated. Knowing how a swimming pool works greatly improves safety. Long haired individuals must avoid water inlets. These inlets, also known as skimmers, are rectangular holes on the wall that are sometimes partly or completely underwater. In private pools there can be one to two inlets, in public pools five to twenty. Also to be avoided are the main drains, usually identified as round mesh covered objects on the pool floor, as poor design can occasionally cause a safety problem. Building codes and product standards have eliminated these hazards for current designs, but not all pools are up to standard.

Also the bigger the body of water, the greater force it needs to have the water circulating. Stronger water pumps are used on large pools to keep them healthy, so extra care must be taken when swimming along the sides or floor of the pool.

People with recent piercings are advised to keep those from being submerged in pools, to avoid them being infected.

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, especially one indoors (see swimsuit).

Undress codes are also stricter in pools than on beaches: wearing shoes, and a shirt, on a beach is acceptable, but often not in a pool. Indoor pools have stricter undress codes than outdoor pools: in outdoor pools, men are often allowed to wear t-shirts for modesty or for protection from sunburn, but usually not in indoor pools. At beaches, many people swim with clothes on and wear beachwear, but at pools (especially indoor pools) more minimal attire is often worn, such as lycra briefs for men or lycra one-piece tanksuits for women. Swimming with clothes on (for example, as practice for the prevention of drowning, as one might fall off a boat clothed) often results in objections from lifeguards at pools, especially indoor pools. In France, board shorts are usually not allowed for hygiene reasons. In Scandinavian countries and in particular Iceland, rules about clothing and hygiene are especially strict. More recently, dress codes in many pools were relaxed to allow more modesty. Many pool operators allow people to swim fully clothed in clothes they only use in the pool if they shower in these clothes before entering the pool.

For diving from towers perhaps 10 m high, sometimes bathing suits are doubled up (i.e., men will often wear one brief inside another) so that the swimsuit does not rip on impact with the water. While splashing around on beaches, especially on urban beaches, looser fitting bathing attire that is more modest is often worn.

Some public swimming pools have regular hours for nude swimming, and some even require nudity. In the US, until the mid 1970s, many YMCA pools required users to be naked or to have a bathing suit made of materials that will not contaminate the pool; the words often used were "nylon bathing suit or no bathing suit" and "wear nylon or go nude".

See also

• Bather load
• Beach
• Lido
• Pool fence
• Swimming pool games

External links

• How Stuff Works: Swimming pools - Explains how pools work
• Swimmer's Guide - Comprehensive International directory of swimming pools
• Pool and Spa Safety Publications from the U.S. Consumer Product Safety Commission
• The Association of Pool & Spa Professionals (APSP) - leading trade association of the U.S. pool/spa and hot tub industry