Immersed-membrane water treating filtering device comprising means preventing filterable medium backflowing to filter cleaning gas injecting means

A water treating system is provided with a membrane chamber having one or more membranes disposed therein for filtering water. To periodically clean the membranes, there is provided a series of cleaning fluid inlets that permit a cleaning fluid, such as a gas, to be injected through the inlets into the membrane chamber which results in the cleaning fluid cleaning the membranes therein. The cleaning fluid inlets are normally closed and are adapted to open in response to the pressure of the cleaning fluid reaching a certain pressure level.