A system is provided for water purification for a recirculation shower in a transport with a filtration unit, a first backwash line and a second backwash line. The filtration unit is designed to filter used shower water. The first backwash line and the second backwash line are designed to clean the filtration unit with a backwashing. The first backwash line is designed to convey backwash water to the filtration unit. The second backwash line is designed to discharge backwash water from the filtration unit.