Chlorine dissipates into the atmosphere through the water surface. The more surface area, the quicker it will dissipate. Folks who "age" their water for aquarium fish will add aeration stones on an air pump to speed the process. Thousands of tiny air bubbles increases the available surface area geometrically.<br><br>Your sloshing the water back-and-forth between bottles has the same effect. Don't start your sloshing until you've left the container sit for the recommended time to purify the water. Aeration beforehand would reduce the amount of chlorine available to kill organisms. Likewise, be sure to close the bottle to reduce dissipation through the top.<br>