A filter system comprising a safety bulkhead fitting, a cap, a filter, a core, and a first cage, characterised in that: the safety bulkhead fitting including a cage-facing end for engaging the core at a proximal portion of the core and a spa-facing end for engaging a suction line of a spa; the cap for engaging the core at a core distal portion and reversibly securing the filter to the core; the filter with a channel passing therethrough, the core slidably engageable in the channel, wherein water may flow freely through the filter, and after passing through the filter may enter the channel of the filter and then may flow freely from the channel into the core through the safety bulkhead fitting and into the suction line of the spa; and the core comprising: a proximal portion for engaging the safety bulkhead fitting and the core distal portion with the first cage positioned between the proximal portion and the core distal portion, the first cage comprising a lattice-like structure that allows the free flow of water therethrough; a second cage positionable within the first cage towards the core distal portion, the second cage comprising a lattice-like structure that allows the free flow of water therethrough, the second cage configured to receive a cartridge, the second cage comprising an opening at the second cage distal end to allow for easy addition and/or removal of cartridge, the second cage opening accessed by removing the cap; the cartridge being selected from one of a mineral cartridge, chlorine tablets, bromine tablets, and aroma therapy cartridges; wherein as water is pulled through the core it is exposed to the cartridge, and wherein the cartridge may be accessed by removing the cap; and a shoulder positioned toward the proximal portion, the shoulder extending circumferentially from the core for the filter to abut the shoulder. the safety bulkhead fitting including a cage-facing end for engaging the core at a proximal portion of the core and a spa-facing end for engaging a suction line of a spa; the cap for engaging the core at a core distal portion and reversibly securing the filter to the core; the filter with a channel passing therethrough, the core slidably engageable in the channel, wherein water may flow freely through the filter, and after passing through the filter may enter the channel of the filter and then may flow freely from the channel into the core through the safety bulkhead fitting and into the suction line of the spa; and the core comprising: a proximal portion for engaging the safety bulkhead fitting and the core distal portion with the first cage positioned between the proximal portion and the core distal portion, the first cage comprising a lattice-like structure that allows the free flow of water therethrough; a second cage positionable within the first cage towards the core distal portion, the second cage comprising a lattice-like structure that allows the free flow of water therethrough, the second cage configured to receive a cartridge, the second cage comprising an opening at the second cage distal end to allow for easy addition and/or removal of cartridge, the second cage opening accessed by removing the cap; the cartridge being selected from one of a mineral cartridge, chlorine tablets, bromine tablets, and aroma therapy cartridges; wherein as water is pulled through the core it is exposed to the cartridge, and wherein the cartridge may be accessed by removing the cap; and a shoulder positioned toward the proximal portion, the shoulder extending circumferentially from the core for the filter to abut the shoulder. a proximal portion for engaging the safety bulkhead fitting and the core distal portion with the first cage positioned between the proximal portion and the core distal portion, the first cage comprising a lattice-like structure that allows the free flow of water therethrough; a second cage positionable within the first cage towards the core distal portion, the second cage comprising a lattice-like structure that allows the free flow of water therethrough, the second cage configured to receive a cartridge, the second cage comprising an opening at the second cage distal end to allow for easy addition and/or removal of cartridge, the second cage opening accessed by removing the cap; the cartridge being selected from one of a mineral cartridge, chlorine tablets, bromine tablets, and aroma therapy cartridges; wherein as water is pulled through the core it is exposed to the cartridge, and wherein the cartridge may be accessed by removing the cap; and a shoulder positioned toward the proximal portion, the shoulder extending circumferentially from the core for the filter to abut the shoulder.