A purge valve comprising a valve body having a first primary loop port, a second primary loop port, a first secondary loop port and a second secondary loop port is provided. The secondary loop ports are disposed at respective ends or a linear secondary loop portion of the valve body. A primary loop portion of the valve body is formed by a pair of closely spaced tees extending from the secondary loop portion. At least one main valve portion is disposed in a first one of the tees. A drain/venting valve portion extends from the main valve portion. A portion of the secondary loop portion between the tees is shared with the primary loop portion in which flow in a primary loop and a secondary loop are hydraulically separated. A second drain/venting valve portion may be provided in a second one of the tees.