The circulation pump, as its name suggests, makes water circulate through your spa, so that it stays heated, filtered, and clean. Often not that powerful, they are usually capable of running 24 hours a day, but can also operate on timed filtration cycles. They have to be capable of filtering the entire volume of water in the spa several times per day.
A common alternative to a dedicated circulation pump, particularly on older spas, is to use a 2-speed pump which runs on low speed for filtration and heating, and can also be used on high speed for massage jets. Circulation pumps are quieter and more energy-efficient than 2-speed pumps, and if they run 24-hours then they generally keep the water cleaner.
If you need to replace your pump, first look for any indications of its manufacturer and model number. It is not enough to know the make and model of your spa - you have to look at the pump itself. The information on the label of the motor and/or wet end, are your best guides. If you cannot find the exact model you need, try to find a pump of the same type (don't replace a circulation pump with a massage pump, or vice versa!), with a similar power and the same type of thread on the plumbing connections, so that you don't have to modify the pipework of your spa. If in doubt, please send us some photos of the pump that you need to replace.