Diaphragm valves are a type of valve that uses a diaphragm to control the flow of fluid through the valve. The diaphragm is a flexible rubber or metal disk attached to the valve body and covers the opening to the valve. When the valve is opened, the diaphragm moves out of the way, allowing fluid flow. When the valve is closed, the diaphragm seals off the opening, preventing fluid from flowing through the valve. They are often preferred over other valves because they are less likely to leak and are easier to maintain.