Hot Tub Jets & Pumps

Hot Tub Jets and Pumps Another myth that has circulated over recent years is that the more hot tub jets you have the better the therapy which is not entirely true. Although a relatively high number of hot tub jets (30-50 large jets) is therapeutic there is a point of diminishing return. This is because when jet count increases in a hot tub (ie more than 30-50) then the jet size is typically reduced in order to accommodate the increased count. This can also reduce manufacturing costs as a smaller jet is less expensive than a larger jet .
For example, an industry standard size of hot tub is 8ft square which has only so much surface area for jet placement. You could easily put 50 large therapy jets (4”-5” inches in diameter) in a hot tub that size. Any more than that then you must shrink the jets in order to make them fit properly. Also, the per jet cost is reduced when the jet is made smaller.

How Many Hot Tub Jets?

A manufacturer might be able to install 80 small jets for the same cost as 50 large jets and many do it this way to give a higher perceived value to the consumer since more jets sell better to an unsuspecting buyer. Furthermore, smaller jets are less therapeutic than larger jets because the air/water mixture is more of 50/50 ratio or higher (75/25) which causes the jets to become extremely itchy or piercing. This reduced therapeutic benefit and discomfort can make the bathing experience much less enjoyable. Larger jets typically have a much higher water to air ratio making the jet nozzle produce more water volume, thereby, giving the bather a much more therapeutic and comfortable massage.
Jets are rated for a certain GPM. The larger the jet the higher the GPM. Essentially water weighs just over 8lbs to the gallon and a higher volume jet is going to push more water thru and that density is what gives a better, more therapeutic massage. Also a larger jet works a large surface area of the body part it is focused on.
Finally, a hot tub with an excessive jet count will also create higher likelihood for leaks because of the tremendous amount of plumbing/fittings and also drilling excessive holes in the shell can weaken the structure.
Hot Tub Jet Pumps
Directly related to jet performance is pump/motor size. First off, many manufacturers use the term “pump” and “motor” synonymously. For simplicity’s sake we’ll refer to them as pumps. Typically pumps come in two sizes, 48 frame and 56 frame. 48 frame motors are generally smaller and have lower horsepower ratings. 56 frame motors are larger and have a higher horsepower rating.
Hot Tub Jets A simple analogy in understanding pump size might be to think about a car engine. A 48 frame would be similar to a four cylinder and a 56 frame might be more like a six cylinder. Also another way to gauge pump performance is to look at the GPM rating (gallons per minute). Most premium hot tub manufacturers hydro-dynamically balance a hot tub. This means the pump size, length and diameter of plumbing, and jet size are all balanced to achieve optimal pressure and flow.

For example, if a 6hp pump is capable of producing 200 GPM and that pump is powering 15 large, 13 GPM jets with the proper plumbing sizes and distance calculations then that design is considered optimally balanced. This example further reinforces the point made about jet size above in that you could have a 3hp motor that might only produce 130 GPM powering 25 small, 5 GPM jets. Essentially a smaller pump powering more jets is a much less therapeutic system than a large pump powering, fewer, larger jets.
Another important consideration is the design of the pump itself. Most of the hot tub pumps used by hot tub manufacturers come from only a few suppliers which makes the quality of the motors fairly similar withstanding frame and horsepower ratings. However, some of the more cutting edge, premium hot tub manufacturers have gone outside the box and have borrowed technologies from other industries that use more premium pumps/motors such as switchless motors which are longer lasting and higher performance than traditional hot tub pumps.