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A 5-seat hot tub with a cast acrylic shell, supported by a frame structure, showing vents for water circulation and massage
A 5-seat hot tub with a cast acrylic shell, supported by a frame structure, showing vents for water circulation and massage
Outdoor hot tubs
Outdoor hot tubs

A hot tub is a large tub full of water used for hydrotherapy, relaxation or pleasure. Some have powerful jets for massage purposes. Hot tubs are sometimes also known as "spas" or by the trade name Jacuzzi.[1]

In contrast to a typical bathtub, a hot tub is designed to be used by more than one person at a time, with many models accommodating four or more people. Hot tubs are usually[citation needed] located outdoors, although they can be installed indoors. Another difference between baths and hot tubs is that soaps and shampoos are not used in wet-jetted hot tubs (although they can be used in air-jetted hot tubs).

History

The earliest hot tubs were calderas in which hot stones were placed to heat the water.[citation needed] Therma in Ikaria has been a very popular place particularly for hydrotherapy ever since the 4th century BC.[2] The remains of wrecked marble bathtubs along with a pre-historic aqueduct that have been unearthed from this area bear ample testimony of the place's popularity in the ancient times.[2]

In 737 A.D., Japan's first onsen opened near Izumo, Shimane, and centuries later the first ryokan (inns) were built, offering food, accommodations, and soaking tubs called ofuro.

In ancient Rome there were three types of baths: baths at home (balnea), private baths (balnea privata), and public baths (balnea publica). The practice of bathing was so engrained that the Roman legions, during their long occupations in foreign lands, built their own baths at mineral and thermal springs in the newly conquered lands. Examples are found all over Europe.[3]

After the fall of the Roman Empire in 476 and the rise of Christianity, cleanliness was abandoned since the Church considered that the practice of bathing a prelude to forbidden behaviour.[4] At Cluny custom required monks to take a full bath at Christmas and Easter.[5] Private bath-rooms in castles, such as the one at Leeds, could often accommodate multiple bathers.[6] From the 13th century onwards, baths gradually came into re-use, particularly in southern Europe under the influence of the Moors.

In the 1940s hot tubs began to appear in the US, inspired by the Japanese ofuro. Hydrotherapy pumps were introduced by Jacuzzi. Fiberglass shell hot tubs appeared around 1970 and were soon superseded by cast acrylic shells.

Water treatment

Plumbing

The plumbing of the hot tub consists of:

Heating and energy use

Hot tubs are usually heated using an electric or natural gas heater, though there are also submersible wood fire hot tub heaters, as well as solar hot water systems. Hot tubs are also found at natural hot springs; in this case, the water may be dangerously hot and must be combined with cool water for a safe soaking temperature.

Effective insulation greatly improves the energy efficiency of a hot tub. There are several different styles of hot tub insulation: some manufacturers fill the entire cabinet with foam, while others insulate the underside of the shell, the inside of the cabinet, or both. Many manufacturers advertise the superiority of their approach to insulation, but few independent side-by-side comparisons are available. The hot tub pump and hot tub heater represent most of the power consumption in a hot tub and vary in use of power depending on their size.[7]

Energy efficiency of portable hot tubs has been studied by the Pacific Gas and Electric Company (PGEC),[8] leading to industry responses[9] and interest from both the California Energy Commission and Natural Resources Canada.[citation needed] California's portable electric hot tub listing[8] include R values of thermal insulation, and standby watts.[10][11]

In 2019 an update to the ANSI standard for energy efficiency was approved. For the first time, this new standard increases the minimum energy efficiency level for portable spas and inflatable spas.[12] [13]

Hot tub covers have been shown to reduce most of the evaporative losses from the pool when not in use. With this component of heat loss being 70%[citation needed] a cover with even a small R-value is able to achieve as much as a 75% reduction in heating costs when used as opposed to leaving the water surface exposed.[citation needed]

There are several different types of spa covers. Some covers are better for insulation and therefore are lighter on internal parts and energy efficiency. Some examples of covers are insulated, aluminum, rolling, or a tonneau.[citation needed]

Sanitation and water quality

Main article: Swimming pool sanitation

Since some hot tubs are not drained after each use it is necessary to treat the water to keep it attractive and safe. It must be neither too alkaline nor too acidic, and must be sanitised to stay free of harmful microorganisms. Partly due to their high water temperatures, hot tubs can pose particular health risks if not regularly maintained: outbreaks of Legionnaires' Disease have been traced to poorly sanitized hot tubs.[14] Typically chlorine or bromine are used as sanitizers, but salt water chlorination is starting to become more common. Hot tubs should also be periodically shocked, which means oxidizing or breaking down organic material left behind from the sanitizer, as well as non-filterable material such as soap films and perspiration.[citation needed]

Sanitation can also be aided by a non-chemical ozonator.

For aesthetic reasons, and for the sanitizer to work properly, water should be neither too alkaline nor too acidic (low pH). The hardness level of the water, measured as the amount of dissolved calcium, is also important. Insufficient hardness can lead to corrosion and water foaming.[citation needed]

Types

Wooden hot tub on a trailer, Finland.
Wooden hot tub on a trailer, Finland.

Safety

Sitting in water above normal body temperatures can cause drowsiness which may lead to unconsciousness and subsequently result in drowning. The U.S. Consumer Product Safety Commission (CPSC) recommends that water temperatures never exceed 40 degrees Celsius. A temperature of 37 degrees is considered safe for a healthy adult. Soaking in water above 39 degrees Celsius can cause fetal damage during the first three months of pregnancy.[20]

It is also recommended to install residual-current devices for protection against electrocution. The greater danger associated with electrical shock in the water is that the person may be rendered immobile and unable to rescue themselves or to call for help and then drown.[21]

Hot tubs and spas are equipped with drains that can create powerful suction and between 1980 and 1996, the CPSC had reports of more than 700 deaths in spas and hot tubs, about one-third of which were drownings to children under age five. In the same period 18 incidents were reported to the CPSC involving body part entrapment. To reduce the risk of entrapment, US safety standards require that each spa have two drains for each pump, reducing the amount of suction.[22] From 1999 to 2007 there were 26 reports to the CPSC concerning circulation entrapments hot tubs and spas, including three deaths.[23]

In 2001[24] and in 2012[25] the CPSC issued recalls for spa heaters which overheated and caused fires.

The Uniform Swimming Pool, Spa and Hot Tub Code is a model code developed by the International Association of Plumbing and Mechanical Officials (IAPMO) to govern the installation and inspection of plumbing systems associated with swimming pools, spas and hot tubs as a means of promoting the public's health, safety and welfare.[26]

Disease risk

Poorly sanitized hot-tubs have been linked to a number of diseases, principally caused by facultative anaerobic bacteria. Such incidents include hot tub folliculitis and legionellosis.[27][28]

Gallery

See also

References

  1. ^ "Has jacuzzi become a generic trademark?". genericides.org. Retrieved March 2, 2021.
  2. ^ a b Ikaria: The Ancient Spa of Therma in Ikaria Greece, Eastern Aegean, Greeka.com.
  3. ^ Schadewalt H. The history of Roman bathing culture [in Dutch]. Integraal1989;4:25–35
  4. ^ Jackson R. Waters and spas in the classical world. Med Hist Suppl1990;10:1–13.
  5. ^ Braunstein, Philippe, "Toward Intimacy: The Fourteenth and Fifteenth Centuries," in A History of Private Life: Volume 2: Revelations of the Medieval World. Georges Duby, ed. (Cambridge, Massachusetts: Belknap Press, 1988), p. 535-632.
  6. ^ "A Short History of Bathing before 1601: Washing, Baths, and Hygeine [sic] in Medieval and Renaissance Europe, with sidelights on other customs".
  7. ^ "Tips to Improve Hot Tub Energy Use" (PDF). Retrieved 18 October 2014.
  8. ^ a b Pacific Gas and Electric Company (May 12, 2004), Analysis of Standards Options For Portable Electric Spas (PDF), California Energy Commission, archived from the original (PDF) on 2006-10-06, retrieved 2008-09-09 (archived from the original on 2006-10-06).
  9. ^ Katherine Wang and Joshua Keim (September 2007). Turning Up the Heat. Poolspanews.com. Retrieved on 2012-08-10.
  10. ^ "List of portable electric hot tubs approved for sale in California". Archived from the original on Oct 27, 2008.
  11. ^ California's current appliance efficiency regulations. energy.ca.gov (2006).
  12. ^ Megan Geuss (January 13, 2020), Updated hot tub standard could bring surprisingly big energy savings to states, Appliance Standards Awareness Project, retrieved 2020-05-14
  13. ^ ANSI/APSP/ICC‐3 "Permanently Installed Residential Spas" (PDF), American National Standards Institute, January 8, 2018
  14. ^ BBC (12 March 2013). "Stoke-on-Trent Legionnaires' deaths: Report calls for hot tub review". BBC News. Retrieved April 20, 2013.
  15. ^ a b Chahine, Aline (2020-08-13). "9 Types of Hot Tubs to Consider For Your Future Home". Architecture Lab. Retrieved 2021-04-20.
  16. ^ Samaan, Payal (9 July 2021). "What are Acrylic Hot Tubs". Allstate Home Leisure.
  17. ^ "The Best Hot Tubs for the Home". Bob Vila. 2020-10-28. Retrieved 2021-04-20.
  18. ^ Bob Barton (August 2016), Recent Work on the Design and Construction of Air Inflated Structures, Science Direct
  19. ^ What Makes An Inflatable Spa Different From A Regular Spa?
  20. ^ "CPSC Warns Of Hot Tub Temperatures". U.S. Consumer Product Safety Commission. Archived from the original on 11 October 2011. Retrieved 2 December 2012.
  21. ^ "Install Ground-Fault Circuit-Interrupter Protection for Pools, Spas and Hot Tubs" (PDF). U.S. Consumer Product Safety Commission. Archived from the original (PDF) on 15 November 2012. Retrieved 2 December 2012.
  22. ^ "CPSC Issues Warning for Pools, Spas, and Hot Tubs". U.S. Consumer Product Safety Commission. Archived from the original on 2 December 2012. Retrieved 3 December 2012.
  23. ^ "1999–2007 Reported Circulation/Suction Entrapments" (PDF). U.S. Consumer Product Safety Commission. Archived from the original (PDF) on 8 January 2013. Retrieved 3 December 2012.
  24. ^ "2001 Reported Fires Caused by Hot Tubs". U.S. Consumer Product Safety Commission. Retrieved 3 December 2012.
  25. ^ "2012 Reported Fires Caused by Hot Tubs". U.S. Consumer Product Safety Commission. Retrieved 3 December 2012.
  26. ^ 2021 Uniform Swimming Pool, Spa and Hot Tub Code (18 ed.). International Association of Plumbing and Mechanical Officials (IAPMO). February 2021.
  27. ^ "Hot Tub Rash (Pseudomonas/ Folliculitis) | Healthy Swimming | Healthy Water | CDC". www.cdc.gov. 2020-07-01. Retrieved 2021-04-20.
  28. ^ "Respiratory Infections | Healthy Swimming | Healthy Water | CDC". www.cdc.gov. 2021-03-30. Retrieved 2021-04-20.