Spa Pumps and Motors
Since there seems to be a tendency to tout horsepower, perhaps it's best to start with what horsepower is, or how it's determined.
The term horsepower was invented by the engineer James Watt (the same Watt as in "60 watt" light bulb) towards the middle 1700's. The "story" is that Mr. Watt was working in a coal mine with ponies and wanted a way to express the amount of power they exerted. He determined that on average a horse could do 33,000 foot-pounds of work in one minute. As arbitrary as it may seem, this unit of measure has made its way down through the centuries to everything from cars to spa pumps.
Because horsepower is a unit of energy, it can easily be converted to any other unit of energy, and one horsepower is equal to 746 watts. The science of it all is this; The basic equation exists saying Amps times Volts equals Watts. Dividing the Watts by 746 then gives the horsepower of a motor. Sound simple? I wish it were! All of this is based upon the amount of actual work a motor is doing. A 5 hp motor, while capable of producing 5 hp of force, if spinning freely, may be exerting less than 1 hp.
Over the years, spa manufacturers have been putting larger and larger pumps on smaller and smaller motors. At one point, one manufacturer was putting a 3 hp pump on a 1 hp motor. Needless to say, the motors didn't have a very long life span... But they were marketed as 3 horsepower.
To make it even more confusing, there are two ways to rate the hp of a motor. Typically a motor is rated at what's called "running horsepower", or how much energy a motor is capable of producing during normal operation. There is though, something called "break horsepower". To initially start the motor spinning, it has to momentarily exert a great amount of energy. This split second boost of power, termed "break horsepower", is normal, and required to get the motor started. Though it is not the force (horsepower) the motor is capable of normally maintaining, it is not unheard of to be quoted this, as the horsepower of a pump.
While the number given to the size of the pump may sound impressive, what's really important is how the jets feel to you! With the proper design and engineering it's possible to have stronger feeling jets with a smaller horsepower pump, as compared to a poorly designed system with a larger "pump".
Spas with more than one pump are becoming more and more common. Having more than one pump can mean you can have more jets. You also can "turn on" only the jets you want to use at that time. This can reduce both the overall noise of the spa, and the total operating cost of running it, since you don't have to operate all of the jets all of the time.
If a spa has the variety jets and the amount of hydrotherapy you want, the size of the pump isn't relevant. Yet another reason "wet testing" a spa is so important. Bigger isn't necessarily better.
Additionally, an interesting article on the Confusion of Horse Power Ratings can be seen HERE.
In May of 2004 awareness of a class action law suit concerning the fraudulent labeling of motor horsepower came to light. While this lawsuit concerned air compressors, the past labeling of such is not unlike current labeling of spa pumps. Hopefully this suit will eventually aid in "cleaning" up the spa industry. Additional info is HERE.