Bell & Gossett offers various control valves, including Flo-Control valves, Hydrotrol flow control valves, Monflo fittings, and Comfort-Trol zone valves. All of these Bell Gossett valves work in their own unique way to control the flow of water in hot water heating systems. Zone control valves open and close to distribute hot water to different heating zones. Zone control valves are used for either continuous or intermittent cycling operation of the system pump. The valve design permits easy replacement of the seal gland without isolating the valve or draining the system.