Thrush Quad-Chek valves are made from quality cast iron. They stop overheating from gravity circulation in hot water heating system by means of positive closing, precision machined, brass-to-brass seat and check weight. The vertical lift action of the check weight produces a smooth floating application of this unit. Thrush Quad-Chek valves can be installed as an angle, horizontally, or by-pass valve, for system loop temperature balancing. The vertical lifting stem design permits several modes of operation including preventing overheating from gravity circulation, allowing balancing of flow in circuits, allowing gravity circulation or draining of the system, and permitting isolation of system for maintenance.