A hot tub's shell--like a shell on the beach--is a firm, beautiful and often vibrantly colored surface that has been molded to comfortably seat its occupants. Both shells protect their inhabitants from exterior forces, allowing a precise amount of water to circulate within them. While a seashell is formed by nature, a hot tub shell is created through an extremely sensitive and exacting combination of machinery and manpower.

According to many spa manufacturers, the hot tub shell is the single most important component to consider when buying a hot tub. If a hot tub shell develops a leak, crack or bubble, it can be very difficult (if not impossible) to fix and may necessitate the replacement of the entire shell, which is a timely and expensive process. Therefore, it is critical to understand the materials and the process used to create the shell of a spa.

Hot tub shells can be made with a laminate composite, tile, wood or a combination of aluminum and vinyl, but the majority are made with acrylic for three main reasons. First, acrylic is easy to clean; its hard, nonporous surface prevents dirt from accumulating, resists stains and can be cleaned with any chemical sanitizer. Second, acrylic is available in a wide variety of colors and styles, including simulated granite and marble, and has a high-gloss finish. Third, acrylic's unique properties allow it to be heated and then vacuum-formed to a specific hot tub seating mold.

Comfortable seating is a must in a hot tub, but what is cozy to one person can feel awkward to another. Therefore, it is highly recommended that you take a wet test before making a final decision, especially since the shell feels much different in buoyant water than it does dry.

Manufacturers offer a number of seating options--from lounge seats to captain style chairs--that match the way you wish to sit in the spa. If you are above or below average in height, take the time to carefully consider seat choices. You want a seat that places your head comfortably above the waterline and your shoulders below it. Seating configurations are important because they provide many options in the way you use the spa, as well as in determining how many people can comfortably fit in it.

The jets, which create the massaging action by forcing air into the water, are often the main reason for buying a spa. While you may be drawn to spa models with a high number of jets, keep in mind that the placement, type and adjustability of the jets should be also factored into your purchasing decision.

You should decide where you need massage therapy the most. If you have neck pain, make sure that a number of jets are strategically placed to direct the soothing water to your neck.

Also, consider what type of jets you prefer. Some jets force water onto afflicted areas with laser-like precision, while others pulse water across a larger surface area.

If you and another primary user have different aches and pains, make sure that each individual jet can be turned off or on easily. This way, (if you purchase a spa with multiple pumps) you can customize the jets when you are using a particular seat.

The hot tub skirt or cabinet is the exterior "box" that protects the hot tub shell and its components. The cabinet is available in wood, typically cedar or teak, or a simulated wood material.

Most consumers today choose simulated wood skirts because they maintain their pristine appearance longer and do not require the annual sanding and staining of solid wood cabinets.

Undoubtedly, as with your home, it pays to have a well-insulated hot tub. Besides helping to keep the spa water warm and toasty, proper insulation can significantly lower your monthly electric bill and act as soundproofing to the spa's interior parts.

There are three main types of hot tub insulation: full foam, layered and trapped-air. Full foam insulation is essentially filling the spa cavity (the space between the shell and the cabinet) with a thick layer of expandable foam that becomes hard. Full foam is an excellent insulator and also acts to support the spa shell. If repairs are needed, a service professional will remove some of the insulation to reach the hot tub's internal parts.

Layered insulation is the process of installing layers of polyurethane foam between the cabinet and the spa shell. High quality layered insulation uses multiple layers of materials with high insulating values (or R-values). With multi-layer insulation, a spa part can be accessed for service by removing some of the layered sections.

The trapped-air method relies on the same concept used to manufacture thermal window. The perimeter is insulated by trapping air between the spa shell and cabinet.*

Which method is best? A fully insulated hot tub will cost more initially to purchase, but very little to operate each month. A "trapped-air" perimeter only insulated hot tub will cost less to purchase, but may add over $ 70.00 or more a month to your electric bill to operate.

*Comparing the insulating properties of a hot tub shell/cabinet to thermal windows is probably not the best comparison to be made by salespeople and hot tub manufacturers. Even the very best thermal windows do not retain heat in your home as well as an insulated wall. The insulating value of a standard double-pained window is around 2. A standard wood wall, 2x6, with R-19 fiberglass has an R value of around 11.7.

Also, windows and doors can account for around 40% of your electric bill. If you are trying to lower your heating costs wouldn't you choose to have the less windows and more walls with insulation? Of course you would.

Windows are necessary to view the outside and to bring light into our homes-not to insulate our homes. The best insulated home would have no windows and only one door!

Perhaps, a more true comparison can be made for helping you understand how to best preserve heat in your new hot tub. Consider a freezer without full foamed dense insulation. You wouldn't.

The control panel is the brain of your hot tub, and with one push of a button, it will obey your every command. While the average control panel will allow you to adjust the temperature and turn the jets on and off, others have waterproof remote controls that can activate multi-colored water and light shows.

Be sure to select a hot tub with a control panel that is well lit for nighttime soaks and is both easy to reach and easy to read from within the spa. Also, look for a panel that offers some automatic controls, such as an automatic shutoff, which will eliminate costly electric bills if the spa's jets are mistakenly left on.

As the heart of the hot tub, the pumps propel the water for filtration, as well as for jet action. You will also want to consider the type of pump(s) because hot tubs can be run using a combination of several. If your hot tub has a one-speed pump, you will also need a small circulation pump. While the main pump supplies the water pressure for the jets, the 24-hour circulation pump quietly circulates the water and generates heat that is distributed back into the spa. A two-speed pump, on the other hand, handles both the circulation and the water pressure for the jets. It circulates the water on low speed and enhances hydrotherapy on high speed.

Regardless of speed, a second pump can be beneficial if you expect to have all the seats occupied on a regular basis. If you have just one main pump, only a certain number of jets will be able to run at the same time. Depending on the number of jets in your spa, you may want an additional pump for increased jet performance and simultaneous jet operation.

A pump's horsepower is rated in one of two ways: The brake or start-up horsepower is the force required to start the pump. The continuous-duty horsepower is the flow of pressure that keeps the pump running. Less energy is required to operate the pump continuously than to start it. Keep in mind that the higher the horsepower, the higher the electric bill.

The goal in choosing the pumps is to get a balanced system so that the size and type of pump works together with number of jets and plumbing. You want to make sure the pumps have the recommended horsepower for size of your spa and the amount of jets.

Remember that bigger is not always better as a large pump on a medium-sized spa can cause stress on the plumbing system and high operating costs.

The filtration system, which removes dirt and debris from the water, is a key component to keeping spa water healthy and clean. The more filtration the better the water quality will be. More filtration translates into easier spa maintenance for you. 

Most hot tubs have one or more cartridge filters, which need to be cleaned every few weeks. Along with proper filtration, water chemistry must also be maintained to keep the water free of bacteria and other contaminants.

Since the heater controls the temperature in your spa, it is vital to your daily hot tub enjoyment. Because the elements on some electric heaters come in contact with corrosive spa water, the heater can be damaged over time. To protect it, be sure to keep your spa water properly balanced and filtered.

Some heaters use stainless steel or titanium tubes to keep the heating elements from coming in contact with the water. These heaters usually last longer but are more expensive.

A hot tub cover can save you more than money. Like a shield, the hot tub cover stops heat from escaping (thus reducing your energy bills), discourages impurities from entering the water and prevents children and small animals from accessing the water unsupervised.

The most important features to look for in a cover are a high-density foam for structural soundness, a high R-value for sufficient insulation and a longer apron (or side flaps) to ensure that heat does not escape.

In addition, make sure that your spa cover has a locking mechanism and a UL (United Laboratories) or an ASTM International (American Society of Testing and Materials) listing. These certifications show that it has been tested to withstand hundreds of pounds and also that it qualifies as a safety cover.