Backflow preventer and system separator especially for fire-fighting applications

A system separator comprising:

• a backflow preventer including:
• a housing enclosing a main flow conduit;
• a valve seat inside the housing on the main flow conduit;
• a valve body movable relative to the valve seat to close off the main flow conduit together with the valve seat in a closed position and to release the main flow conduit in an open position;
• wherein the valve body is alternately movable between the closed position and the open position by at least one of a pressure difference in the main flow conduit or a force of a spring element;
• wherein the main flow conduit is divided in an area of the valve body into at least one outer flow conduit and one inner flow conduit, and the valve body encloses the inner flow conduit and forms at least one valve-body valve seat on the inner flow conduit and comprises at least one primary and one secondary valve disk, wherein the valve body comprises a valve rod carrying the primary valve disk and on which the secondary valve disk is slidably positioned;
• wherein the primary and secondary valve disks are arranged in such a way that in the closed position the primary valve disk is in sealing contact with the valve seat on the main flow conduit and the secondary valve disk is in sealing contact with the valve-body valve seat on the inner flow conduit, and in the open position the primary valve disk is lifted off the valve seat on the main flow conduit and releases the outer flow conduit, and the secondary valve disk is lifted off the valve-body valve seat on the inner flow conduit and releases the inner flow conduit;
• wherein in addition to an inlet and an outlet, a discharge outlet is provided in the housing, which is connected to the outlet in a flow-conducting manner in the closed position of the valve body and is sealed with respect to the main flow conduit in the open position of the valve body;
• wherein the valve rod is mounted in a bearing support having one or more radial struts in the main flow conduit, and wherein the discharge outlet is provided in the one or more radial struts of the bearing support.