Hot tub

**History of Hot Tubs:**
– Earliest hot tubs used hot stones for heating water
– Therma in Ikaria popular for hydrotherapy since 4th century B.C.
– Japan’s first onsen opened in 737 A.D.
– Roman baths were common in ancient Rome
– Hot tubs appeared in the U.S. in the 1940s, inspired by Japanese ofuro

**Types of Hot Tubs:**
– Portable vinyl-liner hot tubs are cheaper and smaller
– Roto-molded hot tubs have molded seating
– Acrylic hot tubs have a cast acrylic shell and frame structure
Cement hot tubs can be above-ground or in-ground
– Wooden hot tubs are made of redwood or cedar

**Hot Tub Plumbing and Maintenance:**
– Hot tub plumbing includes pressure system, suction system, and filtration system
– Induced air and ozone systems are used in some models
– Filtration system helps clean water
– Different hoses and fittings are used for various systems
– Regular maintenance is necessary to prevent health risks

**Sanitation and Water Quality in Hot Tubs:**
– Hot tub water must be treated to stay safe and attractive
– Chlorine, bromine, and salt water chlorination are common sanitizers
– Non-chemical ozonators can aid in sanitation
– Water pH levels and calcium hardness are important for water quality

**Safety Concerns and Regulations:**
– CPSC reported over 700 deaths in hot tubs and spas between 1980-1996
– About one-third of reported deaths were drownings of children under age five
– Install residual-current devices for protection against electrocution
– US safety standards require each spa to have two drains per pump to reduce suction
– CPSC issued recalls for spa heaters in 2001 and 2012 due to overheating and fires

Hot tub (Wikipedia)

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. Hot tubs may be located outdoors or indoors.

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

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. Unlike baths, soaps and shampoos are not used in wet-jetted hot tubs (although they can be used in air-jetted hot tubs). Home hot tubs are often closer in construction to standard bathtubs, while the construction of a public hot tub often has more in common with a swimming pool, of which it can be considered a type.