The 55 Series is our Heavy-Duty water pump. It provides high volume water flow with reduced pump cycling, thanks to the large five-chamber diaphragm. These models are designed to run on water systems with no accumulator tank necessary, and up to five fixtures! It is also suited for use with a holding tank water system, as may be found in a boat, RV or remote cabin. It provides up to 5.0 gallons per minute. The 55-Series pumps are self-priming, and can run dry without damage, performance reliable and low current. 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. This automatic demand water system pump has a built-in pressure switch, which automatically starts and stops the pump when the faucet is opened and closed.They are easy to install service and winterize