Seaflo 55-Series Diaphragm Pump - 12V DC, 5.5 GPM, 60 PSI with HEAVY DUTY PRESSURE SWITCHSelf priming. 5 chamber diaphragm pump. Built in pressure switch, it automatically turns on and off as you turn your tap on and off. With a built in bypass function, the 55 series is able to reduce rapid cycling and not allow water to flow back from the outlet side to the inlet side of the pump. Tips: The pump cannot work continuously for a long time, otherwise it will overheat and affect its operating efficiency and reduce its performance and service