Patent ID: 8257594

Claim:
A filtration system, comprising: at least one reverse osmosis filtration member connected to a feed line, a tank line, and a drain line; an output line to deliver an output flow from the filtration system; first and second water-on-water vessels each configured to alternate between a service state and a fill state such that when the first water-on-water vessel is in the fill state, the second water-on-water vessel is in the service state, and when the second water-on-water vessel is in the fill state, the first water-on-water vessel is in the service state, each water-on-water vessel comprising a first container and a second container; wherein, for each vessel: in the service state, the first container is fluidly connected to the output line while the second container is fluidly connected to the feed line; and in the fill state, the first container is fluidly connected to the tank line while fluid in the second container is fluidly connected to the drain line; a plurality of valve members; and a control system configured to control the plurality of valve members to switch between service and fill states for the first and second vessels.