Strom 4 Inch Automatic Bottom Suction Cistern Pump - 25GPM, 1.0HP, 115V, 60Hz. The Strom BSP has some very unique features. This includes, automatic start and stop controlled by both a separate pressure and flow switch. The pump will turn on when pressure drops below 45 psi and will stop when flow completely shuts off. The pump will continue to run for 30-60 seconds after the flow has stopped to prevent short cycling. The BSP has a built-in flow inducer to protect the motor when water levels drop in the cistern to allow it to operate in as little as 3 inches of water. The pump is thermally protected and will shut off if it detects low water levels, over and under voltage, and excessive heat build-up. Although a pressure tank is not required, we do recommend a small pressure tank for residential usage to minimize pressure surges. Optional cistern float intake is available.