What Makes a Hot Tub, a Hot Tub? Hot tubs have been used for thousands of years in one form or another. What may have started as hot springs coming from earth’s inner core has turned into a form of luxury, party and backyard relaxation phenomenon. As hot tub popularity has risen so has the technology advancements to support it. In the mid 1990’s hot tubs went from using hot rocks or fire to heat the home made tubs to fully operational self heating tubs with massage jet capabilities. This was done so by the innovation of the Jacuzzi Brothers who emigrated from Italy and played a role in revolutionizing several different areas such as airplanes, agricultural pumps, water crafts and of course hot tubs. Hot tubs work on fairly basic principles of moving liquid, heating it and mixing it with air for the desired effect of hydrotherapeutic massage. A centrifugal pump pulls water from the tub where it may pass through a suction filter before moving to the pump. The water enters the pump as kinetic energy; it comes into contact with a fan like turbine which turns the water into potential energy and shoots it into some tubing at higher pressure. After exiting the pump the design of the hot tub might have it go through a pressure filter as opposed to a suction filter which always comes before the pump. The water then passes through an electrical resistance heater, the same kind used in the home to heat water for bathing. Basically an electrical resistance heater is a cylinder with a piece of metal inside that is heated according the thermostat setting. The water passes through and is heated and passed on to a division in tubing which will take it to the individual jets. Before being returned into the tub the water is usually mixed with air to create a more robust massage. This mixture is controlled from the top side. Two different methods have been used to mix air with water. One is an air pump which pushes air into the water; this requires more power and may further complicate the process. The more efficient method would be to use a Venturi air injector which mixes air and water without assistance of a pump. The water will pass through a piece of tubing which narrows, increasing pressure. The water then passes over an opening creating a vacuum and pulling air from the opening into the water with it, the tubing expands once again and the water air mixture is shot back into the tub. The air is usually taken from within the heating compartment to keep the water from being cooled by exterior temperatures. The components of most hottubs require 220 volts or more for operation. However there are some on the market than can run on a normal 110 volt outlet but they are not recommended if you live in a colder climate where freezing temperatures occur during the year .