2/ Look for hot tubs with standard parts. There are several companies that make readily available high quality parts. The word "EXCLUSIVE", means just what it says. You are excluded from buying parts from other suppliers. If they have exclusive parts that you like, check around to see how much they cost to replace. I certainly would not pay $500 for a heater manifold. Most all the major brands have some ridiculous prices on parts.   All of the manufactures of hot tubs use outside manufacturers for the various parts.  If they buy enough parts, then they can have the parts "bastardized" so that they cannot be replaced with the standard part.   There is no difference in quality between "exclusive" parts and non-exclusive.  In most cases the non exclusive parts are stronger.  One large company places the motor frame on the pump on a 45 degree angle, so that you can't even replace it with a better brand of motor.  You are stuck with an inferior part and "pay through the nose" for it.

3/ Look for hot tubs that are fully insulated and not fully foamed. A fully foamed hot tub is not, by any stretch of science, the most energy efficient hot tub. Spas that capture the heat from the equipment and keep cold air off the components and plumbing are efficient.  A fully insulated hot tub has foam on the shell, warm air chamber, and the walls of the cabinet have foam boards. The cabinet is closed with no vents that allow cold air to enter the cabinet except by vacuum. DAIT Click Here

4/ Look for hot tubs with acrylic backed by vinyl ester bonding resin and hand rolled fiberglass with glass cloth or chop. This is the shell with the most history for strength, reparability, and beauty. (When something better comes along I'll be the first to let you know.)   The cheaper hot tubs will use a composite of Acrylic and ABS, or another plastic and ABS with no structural fiberglass.  Then the cabinet is stuffed with structural foam to hold it up.  This is a cause of many problems that result in expensive repairs and more expense to heat the water.

5/ Look for quality electronics. Right now Hydro Quip Gecko and ACC make the best (in my experience) and Balboa is very good, but not with plastic boxes.  The safest is to use steel boxes.  If you put a 50 amp or a 60 amp sub panel in your home, you would never pass code if the panel was made of plastic for fire reasons.  Steel is by far best container for electrical panels and control boxes.  Aluminum is OK but not as safe as steel. (We have always used steel or aluminum, and in 10 years we have had three boxes with electrical arcing.  You could not even see the evidence of it until the box was opened. Then you saw all the black and melted parts. This can happen in any control box. You do not want any power junctions exposed outside of a metal housing. This stops the possibilities of fire.)

6/ Look for hot tubs that have good clean plumbing. If the pump can put out 200 gallons per minute and it is running at 150, there is something wrong with the design. If a diverter valve is used, make sure it is NOT the first thing the pump hits in the plumbing path. If the diverter valve is the first plumbing part after the pump, then the hot tub is poorly plumbed. I call this "diverter first" plumbing. Look for few turns in the main plumbing. A poorly installed diverter valve means that people have to wait their turn for the jets. The diverter valve is similar to driving you car with the brakes on, in which the engine works harder to do less work. If you cannot run all the jets at full pressure at the same time, then the hot tub has a diverter valve, restricting the flow. 

7/ Look for bypass filtering with check valves on the main jet pumps. This insures proper water flow to the jets.  It also follows the ANSI standards for safety.   (The worse design is the no bypass plumbing on hot tub pumps because it limits the water flow and as the filters get dirty, the jet pressure drops. These hot tubs have weak jet pressure to begin with and water diverters.) 

8/ Look for pumps that are mounted to reduce noise. We use rubber mounting pads, solid 2 x 4 frames and lag screws to hold the pumps solid and get rid of "sounding boards" (thin plywood or plastic). Listen to the pumps running on high with all the equipment going. If you can't have a conversation, don't buy it. All you should hear is water! 

9/ The length of a warranty on the hot tub should not be the primary reason for buying. Warranties are hidden "insurance policies" in the hot tub that you are paying for. It is built into the price of the hot tub. For instance, our least expensive hot tubs have a one year parts and labor warranty for a reason. It is to make them affordable. Our high end hot tubs have 5 years parts and labor. The same brand of components, same shell construction, same plumbing parts brands. ( When I hear a salesperson say: "we put our money where our mouth is". They mean "we put your money in our pockets and manipulate the interpretation".) 

10/ Look for reasonable prices. A cheap shell stuffed with foam to hold it up with a one horsepower (1.65 hp), one speed jet pump hot tub with no air jets (air injection) being sold for $7000 is a rip off.  (We have better ones for $3500) Look for the features per dollar of the hot tub as well as design and  construction materials.  Do not purchase any hot tub that you do not understand about the equipment being used.  Find out the real HP, motor size, brand of motor, brand of electronics and jets.  Don't fall for fake awards

11/ Avoid hot tubs that use a tiny 24 hour circulation pump that produces less than 18 GPM. (Unless of course you want to buy scum balls, scum bags, scum bug, extra shock and water clarifiers, and enzyme treatments to help get the scum out of the water.)

12/  Look for hot tubs with a flat surface on the upper shell.  I hate to sit up on hard rounded or convoluted shells. It hurts my butt!!   At some point you are going to want to sit up on the shell and cool down, especially in summer.  I have been using hot tubs for nearly 30 years and I hate rounded upper shells and would NEVER own one. If there isn't multiple places to sit then don't buy it. The worst is Beachcomber with the stupid hand grips all over the top of the shell. The round ones simply put pressure on your bottom and it hurts.  We put large flat areas on our spas on purpose.  It also gives a table to place drinks as well as a serving area over the filter.

13/ Don't be "sold" on a hot tub by a salesman. If you feel pressure and manipulation, get up and walk out. The deal they have now that is so good, may be even better tomorrow. Research the products and take some "salt" with you so you can take everything as they say with "a grain of salt". Make your decision to purchase at a later time based on knowledge. ( There is a company that goes around with trailers and RV's with a sign on the trailer saying "LIQUIDATION SALE". The hot tubs they sell are lacking in cold weather insulation, not fully finished, and are being sold for about $1000 more than a comparable hot tub. They say if you don't buy now, you will miss out on the best deal. They also don't take care of the customers. They are unethical. This is the epitome of high pressure sales.)  If you go to a home show, you need to know about hot tubs and prices before you go, otherwise, you most likely will be taken advantage of.  HOME SHOW WISDOM CLICK HERE

14/ Buy hot tubs that are ANSI/NSPI(Click here) conforming. The largest manufacturer of portable hot tubs does not follow these engineering design rules.   These rules are their to protect consumers and are not subject to interpretation.