Hot Tub Hub

This style of hot tub is constructed with wooden staves and steel bands, very much like a very large barrel. The staves are usually made of redwood, cedar, or teak, with most historic tubs made of redwood. Wooden hot tubs are often quite deep, 36"-48", and are inset within a wooden deck for ease of entry. Inside the tub, wooden bench seating is common, forming a ring around the inner circumference of the tub.

One piece spas

Using a crane is a common method of installing a one piece hot tubOne piece spas, also known as unibody spas, are formed as one piece with shapes that provide a variety of seating arrangements within the tub. Each integral seat is often equipped with one or more water jets that allows water to be directed at parts of the body. The water flow may be aerated for additional effect, and some or all of the jets may also automatically move or rotate, providing a massage-like effect. Although wooden tubs were the most common type of hot tub in the 1970s, one-piece hot tubs now dominate the market as they are less expensive to manufacture, easier to install, and more energy efficient. In America, these kinds of tubs are also referred to as Jacuzzi or Whirlpool tubs, though both are brand names.

One piece spas are usually shallower than wooden tubs, usually being 32" to 36" in height to fit through doors and narrow hallways. Cranes are occasionally used to place one piece spas in a backyard or other location that does not have adequate clearance for carrying the tub.

Spas usually have at least two water pumps, with one small circulator pump serving the heating and filtration water loop and the other(s) driving the hydrotherapy jets. Sophisticated computer controls are now common and many tubs now are equipped with extensive lighting, sound systems, and even flat-screen televisions with DVD players.

The spa shell is the exterior of the tub, and is composed of a surface and an understructure that are bonded together during the manufacturing process. The surface is the source of the color, look and feel of the spa, so it should resist deterioration due to the sun, spa chemicals, or normal wear and tear. Some high-end shells have special coatings to make them more stain resistant or have anti-bacterial ingredients molded into the shell material.

There two primary methods used for manufacturing one piece spa shells:

vacuum forming of an acrylic base by placing the sheet over a mold and heating with an overhead heater while pulling a vacuum on the mold
rotational molding: involves placing polyethylene powder in an aluminum mold which is then heated and spun in a large oven so that the plastic melts and takes the form of the mold.
The understructure of the shell provides the strength needed to support hundreds of gallons of water and the weight of the bathers (the cabinet is not normally part of the weight-bearing structure). The substructure is generally made of FRP (commonly called fiberglass), though some companies use ABS or other plastics. Some manufacturers build a self-supporting shell, while others use secondary supports of wood or metal under the seats or in high-stress areas to reduce the amount of FRP required. Some companies use a perimeter frame of wood or metal to support the rim.

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.
The spa cabinet is the skirting around the hot tub, and serves as both an enclosure for the plumbing and a decorative wrap. For many years, spa cabinetry was made of wood, most commonly redwood or cedar, and this is still a popular choice. Wood cabinets require regular maintenance, though, especially in climates where they are exposed to severe weathering. Synthetic materials are increasingly popular because they are seen as requiring relatively little maintenance to keep their appearance.

Effective insulation greatly improves the energy efficiency of a spa. There are several different styles of spa 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. Both the California Energy Commission and National Resources Canada have taken an interest in the energy efficiency of portable spas (late 2006).