Hot tub

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

A hot tub is a large tub or small pool full of heated water and used for pleasure or hydrotherapy. Some have jets for massage purposes.

In contrast to a typical bathtub, a hot tub is designed to be used by more than one person at a time and is usually located outdoors. Also, the water is not changed with each use, but is kept sanitary using similar methods as swimming pool sanitation.

Hot tubs are sometimes also known as spas or by the trade name Jacuzzi.^{[citation needed]}

Water treatment

Plumbing

The plumbing of the hot tub consists of:

• A pressure system delivering water to the jets
• A suction system returning water to the pumps.
• A filtration system: the plumbing has to incorporate a filter system to help clean the water. Some models use a separate small 24/7 filter pump while others use programmed settings of the main pumps.
• Induced air: The jets may use a venturi effect to incorporate air into the water stream for a lighter massage effect; this requires another set of hoses.
• Some models use an air blower to force air through a separate set of jets for a different "bubbly" massage effect; this is a separate system from the induced air.
• An ozone system: ozonation is a common adjunct to water maintenance, and if installed will have its own set of hoses and fittings.

Heating & 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. Not surprisingly, 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.^{[citation needed]}

Energy efficiency of the tubs has been studied by the Pacific Gas and Electric Company. The industry has responded to the study.

After this study, both the California Energy Commission and National Resources Canada have taken an interest in the energy efficiency of portable hot tubs (late 2006).^{[citation needed]}

California's portable electric hot tub listing include R Values of thermal insulation, and standby watts.

Hot tub covers have been shown to reduce most if not all of the evaporative losses from the pool when not in use^{[citation needed]}. 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 hot tubs are not drained after each use one must be careful 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. 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 your sanitizer, as well as non-filterable material such as soap films and perspiration.

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 water, measured as the amount of dissolved calcium, is also important. Insufficient hardness can lead to corrosion and water foaming.

Types of hot tubs

• Portable vinyl-liner hot tub: these are cheaper and smaller, and require less power, e.g. 110-120V 15A household power circuits in North America.
• Roto-molded hot tubs are constructed with the shell and surrounding cabinet as a single piece. They have molded seating.
• Acrylic: these hot tubs have a cast acrylic shell, supported by a frame structure, and are usually surrounded by a skirt of either cedar or simulated wood-grain plastic. They typically can seat two to seven persons or more.
• Cement: hot tubs can also be built of cement, above-ground, or in-ground like a small swimming pool.
• Wood hot tubs: round wood hot tubs peaked in popularity in the 1970s, having now been replaced by modern construction methods. Wood hot tubs are often made of redwood or cedar and assembled from vertical staves and the structure is held together like a wooden barrels, with metal bands.

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 104 degrees Fahrenheit. A temperature of 100 degrees is considered safe for a healthy adult. Soaking in water above 102 degrees Fahrenheit can cause fetal damage during the first three months of pregnancy.

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.

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 intakes for each pump, reducing the amount of suction. From 1999 – 2007 there were 26 reports to the CPSC concerning circulation entrapments hot tubs and spas, including three deaths. In 2001 and again 2012 Dec 2001 UPSC and 2012 Watkins Products, Hot Spring spas has had recall for safety problems with heaters catching fire. Again 2012 Watkins spas cathing fire;

Gallery

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  Bathers enjoying a hot tub in the winter in Keystone, Colorado

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  Wood-fired hot tub at the Adirondack Canoe Classic, Saranac Lake, NY

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  A hot tub at the Big White Ski Resort, Canada

See also

• Finnish sauna
• History of spa filters
• History of the hot tub
• History of water filters           
• Ofuro
• Sauna
• Steam shower
• Turkish bath

External links

• Images of hot tubs at Wikimedia Commons