Experience has shown that a single step water-conditioning process cannot be used to prepare Bashkirian produced waters for underground injection. In the single-step process, the water is passed through horizontal or vertical settling basins to remove solids. This system does not work when suspended solids increase above 200 to 500 mg/liter. The required quality of injection water can be obtained by filtering the water through sand at flow velocities of 5 to 10 m/hr. The filter has a sand layer 0.6 to 1 m thick, composed of 0.35 to 1.0 mm sand. Water entering the filters should not contain more than 100 to 150 mg/liter of oil products. The filters are backwashed at velocity of 10 to 15 m/hr and rates of 12 to 16 liters/sec sq m for 10 to 15 min. Clean water is used in backwashing. When surfactant is added to the backwash water, the filter cycle lasts longer.