A heated tub is usually thought of as a luxury item that only wealthy people own. That may have been true at one time, but in contemporary homes, they are often found in ordinary living quarters that people enjoy. They are mainly used for relaxation and water therapy.

The two common styles of hot tubs are wooden-staved tubs used for soaking, and one-piece tubs made of plastic. Many of the currently manufactured units have heaters with solar water heating systems. Tubs found at nature’s hot springs are often so hot they are a hazard and must be mixed with cool water for safety.

Wooden hot tubs are made with wooden segments and bound round with bands of steel. They resemble an unusually large barrel. These tubs are quite deep and are often set within the floor of a wooden deck with wooden bench seating inside.

One-piece heated baths, or spas as they are often called, are made as one piece with a variety of shapes that offer different seating within. Each of the seats has several water jets so the water can be directed to a variety of body areas. The one-piece wooden units were the most in demand in earlier times. The one-piece version is now the most popular, since they are less expensive to make, installation is easier and they are more energy-effective.

Insulation is an essential part of a spa or heated vessel and has a large bearing on how energy efficient the unit operates.

Sanitation is another aspect of having a bath with water heaters at high temperatures and chemistry is also necessary to alleviate disease and/or damage to the unit. Also, a pump and particulate filter are essential for a sanitary cask as well as bromine, chlorine and other sanitizers. Maintaining the chemistry of the water includes the pH, alkalinity and calcium firmness within tolerable limits.

The heated tubs and spas were improvised by the Greeks. Greek celebrities were acclaimed for invention of these heated baths of thermal and mineral water as early as 500 BC. The baths were found mostly near natural warm springs and sometimes near volcanoes. Here, the wealthy Greeks would treat their physical ailments such as rheumatism, jaundice and others.

The Romans also discovered and enjoyed the heated natural mineral and thermal baths. They even gave the baths valid names, such as Caldarium, Tepidarium and Frigidarium, which suggest the temperatures of the water from extremely hot to lukewarm to cold. The Emperor was yet unable to fit a bath into his home or on the balcony.