Basement Watchdog BW4000 1730 Gallons Per Hour Combination Primary and Back-Up Pump System Package contains: Controller, charger, two dual micro reed float switches, primary pump and backup pump, instruction manual (battery and acid sold separately) Back-up starts immediately after loss of power or if flow of water is too great for the AC pump alone Back-up features unique monitoring systems to diagnose problems and sound an alarm Compact, fits in pits as small as 12-Inch in diameter.