This is a replacement valve for a dual tank, or twin tank application. The 9100 SXT digital twin tank valve connects two water softener tanks for automatically alternating between tanks as needed. Metered control measures water use and will switch tanks and regenerate as needed to ensure continuous soft water around the clock.---Digital easy to use controls provides efficiency and easy use with LED readout, touch pad controls. Fully adjustable 5-cycle control delivers controlled upflow backwash, downflow brining, slow rinse, rapid rinse, timed brine refill and downflow service Perfect for light commercial/heavy residential systems that require twin tank conditioning capabilities Continuous flow rate of 21 GPM All cycles are easily adjustable; program only necessary functions with "all cycle" variable time control Backwash capacity handles tanks up to 16" Choice of 3/4" or 1" meter satisfies wide range of operational needs Valve delivers continuous softened water Salt and water savings by using 100% capacity of the tank in service before switching to the second tank Regenerates immediately when needed for continuous soft water Regenerates with soft water and keeps system clean for optimum operating efficiency and minimum maintenance----- This does not come with the bypass valve or the 2nd tank adapters. If you need these parts for a new application, please contact us or see our other listings for the bypass valve if needed. Full warranty and support