The GLB Filter Rinse is an effective sand filter backwashing aid that is very easy to use. In just one step, simply pour it in the skimmer during the backwashing process and watch the caked up contaminants wash away. After using this liquid formula, the sand filter particles in the filter housing will be rejuvenated and work at a higher efficiency. The GLB Filter Rinse is a necessary product to maintain crystal clear water in pools that use a sand filter. Filter Rinse is compatible with chlorine, bromine, ozone, and biguanide sanitizers.