Reverse Osmosis (RO) filters use membrane technology to filter impurities such as minerals, calcium, chloride, sodium, and chlorine from the water. The systems require periodic backwash to clean the filter. This discharge water is usually directed to the sewer drain line, but it can be recovered and used. Since the discharge water from an RO system is only slightly less pure than the source water entering the filter, it can be well within safe drinking water standards and certainly suitable for irrigation or other alternate reuse applications.