Clean water from the Clariflocculator enters the Sand Filter from the top. The Filter contains several layers of specialty sand of different corseness. As the water travels through the sand, the remaining particles or comtaninants are trapped by the layers of sand. The clean water travels out the bottom of the Filter and into the Chlorine Contact Chamber. The Filter has a series of valves and pumps so when the Filter becomed dirty or plugged, the flow to the Filter can be shut off. Pumps push water upward through the sand Filter and backwash the dirt into a holding tank. Once the backwash has completed, the filter returns to normal operation.