Use only sodium chloride (NaCl) salt that is at least 99.8% pure. It is also possible to use salt pellets (compressed forms of evaporated salt) for water treatment. However, they take a longer time to dissolve. Do not use iodized or yellow colored salts (yellow sodium cyanide). We also do not recommend the use of unpurified sea salt - this contains many minerals that clog the hot tub's system and can cause various defects. Salt is added to the water and the saltwater system uses the salt to create chlorine. The purer the salt, the better the performance of the saltwater system.