Unlike most portable spas, which typically use a filtration system integrated into the skimmer, these filters are designed to installed separately in an equipment area.
Top-Load models allow you to remove the filter cartridge from above (hence their name) to change and/or clean it without allowing dirt back into the system.
These filter housings have an integrated bypass valve that opens when the water pressure is high. The system is ideal for spas equipped with a two-speed pump. The water is fully filtered when the pump is running at low speed, but the valve opens to let some of the water pass without filtration when the pump is running at high speed. This reduces the risk of damage to the filter cartridge, and ensures a strong flow and water pressure at the massage jets.