This invention relates to filter assemblies for filtering water, for example pond or aquaria water.
According to the invention there is provided a filter assembly for filtering a flow of water, the assembly comprising a container enclosing an inlet chamber with an upstream region and a downstream outlet, a filter medium in the inlet chamber between the upstream region and the downstream, outlet, an outlet chamber downstream of the outlet and a valve which normally occupies a closed condition but which, upon internal water pressure in the upstream region exceeding a predetermined threshold, occupies an open condition enabling water to pass from the upstream region to the outlet chamber without passing through the filter medium, the open condition of the valve being visually apparent and thus providing to the user a visual indication of the open condition of the valve, in use the upstream region being capable of resisting rising internal water pressure caused by progressive clogging of the filter medium, until the internal water pressure in the upstream region exceeds the predetermined threshold whereupon the valve opens and the visual indication appears.
The outlet chamber may contain a source of ultra-violet radiation to which the flow of water is exposed, regardless of whether the valve is in the open condition or the closed condition.