a strainer device for filtering water to an emergency cooling system in a nuclear power plant includes a housing or tube having a perforated or apertured strainer wall through which water may flow from the outside and into the interior of the housing in connection with the regular filtration of water taken in . a water - receiving accumulator tank is connected to the cavity of the strainer housing and a source of pressurized gas is connected to the tank in order , if required , to feed pressurized gas into the tank so as to momentarily force water out therefrom and into the cavity of the strainer housing while backflushing the same .