What is the purpose of backwashing?
In backwashing, the water goes down the riser tube, lifts and turbulates the carbon media, and then comes out of the backwash drain line when complete. The tank is filled 2/3 full of carbon, which allows the remaining 1/3 as a freeboard area, allowing room for the carbon to swirl around without being forced out the backwash line. A top screen on the valve head protects the valve head from any carbon lodging in it. Backwashing serves to force out dirt and sediment, prevents bacteria growth, and prevent any channeling or packing by refluffing the carbon bed.
