A filtration system, comprising: at least one water filtration member fluidly connected to a feed line, a tank line and a drain line; an output line; a first water-on-water vessel (14, 114) and a second water-on-water vessel (16, 116) each fluidly connected to the filtration member and configured to alternate between a service state and a fill state, each vessel (14, 16, 114, 116) having a filtered water space (31, 44) and a delivery water space (33, 46); a plurality of valve members (S1-S8, Y004-Y007, Y010-Y013); and a control system configured to control the plurality of valve members (S1-S8, Y004-Y007, Y010-Y013) to switch between service and fill states for the first and second vessels (14, 16, 114, 116), characterized in that for each vessel (14,16, 114, 116): in the service state, filtered water is expelled from the filtered water space (31, 44) of the vessel (14, 16) by opening the flow path to the output line and filling the delivery water space (33, 46) of the vessel (14, 16) with water from the feed line; and in the fill state, the filtered water space (31, 44) of the vessel (14, 16) is filled with filtered water delivered from the filtration member while the delivery water space (33, 46) of the vessel (14, 16) is open to the drain line; and in that the control system controls the plurality of valves (S1-S8, Y004-Y007, Y010-Y013) such that when the first vessel (14, 114) is in the fill state, the second vessel (16, 116) is in the service state, and when the first vessel (14, 114) is in the service state, the second vessel (16, 116) is in the fill state. at least one water filtration member fluidly connected to a feed line, a tank line and a drain line; an output line; a first water-on-water vessel (14, 114) and a second water-on-water vessel (16, 116) each fluidly connected to the filtration member and configured to alternate between a service state and a fill state, each vessel (14, 16, 114, 116) having a filtered water space (31, 44) and a delivery water space (33, 46); a plurality of valve members (S1-S8, Y004-Y007, Y010-Y013); and a control system configured to control the plurality of valve members (S1-S8, Y004-Y007, Y010-Y013) to switch between service and fill states for the first and second vessels (14, 16, 114, 116), characterized in that for each vessel (14,16, 114, 116): in the service state, filtered water is expelled from the filtered water space (31, 44) of the vessel (14, 16) by opening the flow path to the output line and filling the delivery water space (33, 46) of the vessel (14, 16) with water from the feed line; and in the fill state, the filtered water space (31, 44) of the vessel (14, 16) is filled with filtered water delivered from the filtration member while the delivery water space (33, 46) of the vessel (14, 16) is open to the drain line; and in that the control system controls the plurality of valves (S1-S8, Y004-Y007, Y010-Y013) such that when the first vessel (14, 114) is in the fill state, the second vessel (16, 116) is in the service state, and when the first vessel (14, 114) is in the service state, the second vessel (16, 116) is in the fill state. in the service state, filtered water is expelled from the filtered water space (31, 44) of the vessel (14, 16) by opening the flow path to the output line and filling the delivery water space (33, 46) of the vessel (14, 16) with water from the feed line; and in the fill state, the filtered water space (31, 44) of the vessel (14, 16) is filled with filtered water delivered from the filtration member while the delivery water space (33, 46) of the vessel (14, 16) is open to the drain line; and