Saltron® Mini Spa Sanitation System produces a pure form of chlorine by electrolysis of salt (NaCl) in order to sanitize your spa water. After the salt is converted to chlorine and the bacteria are killed, the chlorine converts back to salt and this process is ongoing. The salt concentration used is very low (less than that in a human tear). Chlorine output can be easily adjusted by the timer on the power supply unit. The chlorine level in your spa can be checked by using a standard chlorine test kit. One Saltron™ Mini unit can treat up to 600 gal of spa water (or up to 2000 gal Swim Spa water)