Some water filtration systems may require you to buy a separate water filters however the Conventional water softener devices are being used where the water passes through a bed of the resin. The resins containing univalent hydrogen, sodium or potassium ions, exchange with divalent calcium and magnesium ions in the water and the resin help in removing carbonate, bi-carbonate and sulphate ions which are absorbed. Such filtration system may be desirable when the source of water is from a well, whether municipal or private water source.