Abstract: A leak testing device to be positioned adjacent one or more conduits comprises a generally cylindrical body defining a recess therein and including first and second end portions for cooperating with an end portion of a conduit. The body includes an opening between the first and second end portions. A sealing door or a test door is selectively positioned in the opening. A diaphragm member including a through hole is provided to be positioned within the body. A valve is operably connected to the diaphragm member for selectively opening or closing the through hole to thereby permit or restrict the flow of a fluid therethrough. A window for viewing the interior of the body for troubleshooting, diagnosis, etc., may optionally be provided. The opening in the body receives the diaphragm member and the test door when leak-testing a conduit, or the sealing door when connecting one or more conduits in a fluid communication.