In North America it is law for any commercial establishment to have a closed pressurized filtration system on any public pool or Hot Tub. Not only is it more efficient and faster than a skim filtration system but it also removes the dirty filter canisters from the bathing area.
Without a pressurized system, once the water flow to the filter subsides, the debris that was caught in the filter is free to float back into the spa and re-contaminate the water. We like this idea about as much as sitting in the water with the dirty filters. So Coast Spas developed the Hydro Cyclonic Filtration System®. This is a commercial-grade, pressurized filtration system with the filter canister completely removed from the bathing area and coupled with an oversized skimmer.