Spa filters work by capturing debris from the water passed through them.
Simply stated, filters with large surface areas collect more debris. Large hot tub filters reduce the number of impurities and particles that are pumped back into the hot tub's water. As you're shopping for the best hot tubs, ask your salesperson about the size of filter used in the hot tub, and how that size relates to other hot tubs on the market.
Some hot tubs come with more than one filter. While their areas combined may be the same size as one larger spa filter, you'll have to clean more than one filter, so make sure filters are easy to access and remove.
The amount of water that passes through a hot tub's plumbing is one of the true tests of a filtration system. It is important that all of the water in the hot tub is filtered several times each day. Of course, this is most important when you need it the most: when you're sitting inside the hot tub.
Many hot tubs come with pre-programmed hot tub spa filters. Depending upon the price of the hot tub and the complexity of its internal control system, you may be able to program your own cycles, or choose one of several pre-set cycles. These cycles determine the number of times per day your filter cycles will activate and the length of each cycle.
During a filtration cycle, the jets in your spa will turn on and water will be rapidly pushed through the filter. Filtration cycles are generally set depending upon "bather load" (a measurement of how often you use your hot tub or spa).
Make sure to inquire about filtration cycles. How often is all the water filtered? Remember that filtration is a gradual process. If the hot tub you're considering holds 250 gallons of water, it is important that the hot tub can filter at least 10,000 gallons of water per day!
Many hot tubs offer circulation pumps. A circulation pump keeps a small amount of water moving through your hot tub filter continuously - day and night. While circulation pumps do not work alone, they are effective in helping to keep your water clean and clear because they prevent standing water. In conjunction with powerful filtration cycles, they can help ensure that your water is adequately filtered all day long.