I would reprogram the valve for a 10 minute backwash, 0 minute brine and rinse, and a 4 minute fast rinse. The fast rinse helps remove the dirty water that was used for backwashing and replaces it with filtered water. The fast rinse can be reduced to the tanks water volume at a minimum, on a birm system that is usually around 4 minutes. You can reprogram the valve to a ST1B (single backwash) and it will be fine. The softener piston does fine for a filter valve, but the standard piston for backwashing has a limited backwash rate.