Water from the recarbonation basin passes through four open, gravity-flow filtration beds which operate in parallel. Filtration reduces turbidity. Each filter has a design capacity of 3.75 MGD at a rate of five gallons per minute per square foot of surface area. The filters provide coarse to fine filtration in the direction of flow. The filter media are anthracite coal, silica sand, and fine and coarse garnet. Combined, they are 30 inches deep and are supported by a bed of gravel and a tile block underdrain system. A typical filter run generally exceeds 100 hours. The filters are backwashed at the rate of 15 gpm/ft2 from the filter effluent sump.

Following filtration, the flow is split into two parts, with roughly two thirds of the water going to granular activated carbon adsorption and one third bound for treatment using reverse osmosis.