Leisure Time's Renew is a non-chlorine shock treatment that is a fast-dissolving granular which rids spa water of residual soaps, deodorants, natural oils and organic materials that can build up in spa water. When Renew is added to the spa water, it reacts with the bromide and forms a bromine solution to destroy any microorganisms left behind by the bather. Part of the Reserve & Renew Chlorine-Free Sanitizing System.