The filter removes turbidity, colour and odour from the water as it passes through the filter container. The particles get stuck in the filter mass, carbon and sand, which after a while may need backwashing to avoid duct formation in the filter bed. This is easily done with a manual valve that is turned from filtration to backwashing. The bed needs to be replaced when it is saturated and this is noticeable by the problem being back in the taps.