Rubber Ball - Used to regulate flow behind backwash plug and brine control dial.
Old part number 4F, and newer part number 1030502 ( cross reference = 622014 )
Chlorine in the water supply can cause this part to swell and soften to the point that it will either block normal flow
or get stuck and allow too much flow.
The ball behind the Brine Control Dial and the Back Wash Plug are identical.
NOTE: The Ball is often REMOVED ( left out ) if the valve is used to Backwash "heavy media" ( like Greensand, or Calcite ), to allow higher flow rates. The Ball is used to "limit" the flow rate in conjunction with the slots on the Backwash Plug for Softener Resin, and smaller Carbon filter applications, but again, not used with valve modified for Greensand, Birm, Calcite, Katalox, etc.
***** NOTE: Do not confuse this ball with the larger ball used in the Ball New Style Aircheck - 1030528