Holding Tank Systems: BLACK WATER: Add 30 ml for each 19 liters of tank capacity. Pour through toilet into holding tank and add 4 liters of water. Hot weather and long retention times may require additional treatment. GREY WATER: Use 30 ml for each 38 liters of tank capacity. Pour through shower or sink drain and add 4 liters of water. RECIRCULATION TOILETS: Pour 236 ml into initial water charge. PORTABLE TOILETS: Pour 118 ml into waste holding tank and add water to cover tank bottom.