Designed to bring pumping power to tight spaces, the Rule LoPro Series bilge pumps are only 2.4" (6cm) high. The LP900S model features two automated modes. The first one engages the pump when the water level reaches 2" (5cm) or 1.3" (3.25cm) (user choice); and the second one checks for water by briefly turning on the pump every 2-1/2 minutes. The LP900D model uses a traditional float and/or panel switch for operation.