How does it work? - You add 3.5 lbs of sodium bromide into the spa water. The sodium bromide separates into sodium ions & bromide ions. As the spa water is pumped through the electrodes in the bromine generator the bromide ions are turned into the bromine sanitiser. That sanitiser performs it’s function before turning back into bromide ions and the process repeats. The bottom line is that you add the 3.5 lbs of sodium bromide once and that’s it ... until you drain and refill your spa ..