A water treatment system is provided, including a raw water tank connected to a water supply, a reverse osmosis unit arranged to produce purified water from water input from the raw water tank via a raw water supply line, at least one water treatment facility alongside the raw water supply line downstream of the raw water tank and upstream of the reverse osmosis unit, and a reuse water feedback line arranged to feed waste water and/or grey water collected from the reverse osmosis unit and/or the at least one water treatment facility back to the raw water tank for reuse. In a water treatment method in such a water treatment system, waste water and/or grey water collected from the reverse osmosis unit and/or the at least one water treatment facility is fed back to the raw water tank for reuse.