A reverse osmosis system in fluid communication with a fluid reservoir comprising: an elongated pressure vessel having a membrane therein, a fluid input (108, 110), a permeate output, a brine output, the elongated pressure vessel having a first end, a second end and an outer wall; a high pressure valve having a first open state and a first closed state; a low pressure valve having a second open state and a second closed state; a high pressure pump in fluid communication with the fluid input through the high pressure valve; and a low pressure source (124, 210) in fluid communication with the fluid input through the low pressure valve, said high pressure pump and said low pressure source in fluid communication with the fluid reservoir, wherein said low pressure source is configured to fill the pressure vessel through the low pressure valve and said high pressure pump being configured to operate during permeate production through the high pressure valve wherein the fluid input is disposed proximate the first end; a flow tube having a first flow tube end proximate the first end and a second flow tube end proximate the second end, said flow tube disposed within the pressure vessel to form an annular space between the flow tube and the outer wall; wherein the membrane is disposed within the flow tube opposite the first end of the pressure vessel, said membrane producing permeate fluid and brine fluid; and a flow diffuser connected to the fluid input and disposed within the pressure vessel; a distributor plate disposed within the flow tube; a recirculating pump having an impeller recirculating brine fluid between the outer wall and the flow tube, said impeller disposed within the flow tube proximate the second flow tube end so that the brine fluid enters the flow tube and distributor plate from between the flow diffuser and the flow tube toward the first end of the pressure vessel. an elongated pressure vessel having a membrane therein, a fluid input (108, 110), a permeate output, a brine output, the elongated pressure vessel having a first end, a second end and an outer wall; a high pressure valve having a first open state and a first closed state; a low pressure valve having a second open state and a second closed state; a high pressure pump in fluid communication with the fluid input through the high pressure valve; and a low pressure source (124, 210) in fluid communication with the fluid input through the low pressure valve, said high pressure pump and said low pressure source in fluid communication with the fluid reservoir, wherein said low pressure source is configured to fill the pressure vessel through the low pressure valve and said high pressure pump being configured to operate during permeate production through the high pressure valve wherein the fluid input is disposed proximate the first end; a flow tube having a first flow tube end proximate the first end and a second flow tube end proximate the second end, said flow tube disposed within the pressure vessel to form an annular space between the flow tube and the outer wall; wherein the membrane is disposed within the flow tube opposite the first end of the pressure vessel, said membrane producing permeate fluid and brine fluid; and a flow diffuser connected to the fluid input and disposed within the pressure vessel; a distributor plate disposed within the flow tube; a recirculating pump having an impeller recirculating brine fluid between the outer wall and the flow tube, said impeller disposed within the flow tube proximate the second flow tube end so that the brine fluid enters the flow tube and distributor plate from between the flow diffuser and the flow tube toward the first end of the pressure vessel.