Every flow- or surge-control valve consists of a valve body to convey (and sometimes redirect) flow and a piston to open, restrict, or block flow. Since all valves can cause a sudden stoppage of flow, resulting in hydraulic transients if closed too quickly, it is important to know how each type operates. The following paragraphs summarize key characteristics for each type:

Butterfly valves are very common in water systems, primarily for on-off and throttling service. A circular disc or vane pivots around an axis at right angles to the direction of flow in the pipe. Typically, a quarter-turn is sufficient to open or close this valve. Actuators are often installed to require a large number of turns to prevent rapid closure, sudden stoppage of flow, and the resulting hydraulic transients.

Gate valves are a general-service valve used primarily for on-off, nonthrottling service. A flat face, vertical disc, or gate slides down through the valve to block flow. These valves can be found on very large suction or discharge piping inside most water pumping stations, often equipped with actuators with very large gear ratios to allow manual operation. They may be operated only yearly or less frequently.

Globe valves are used for on-off service and throttling applications. A plug with a flat or convex bottom is lowered onto a matching horizontal seat located at the center of the valve. Raising the plug opens the valve, allowing flow. Many different types of materials and pistons are available, including anticavitation or multi-orifice cages. Globe valves are typically available with a straight-through body or with an angle body that simultaneously turns flow through 90 degrees.

Plug valves are used primarily for on-off service and some throttling. They control flow by means of a cylindrical or tapered plug with a hole in the center that either lines up with the flow path or blocks it with a quarter-turn in either direction. Actuators are often installed to require a large number of turns to prevent rapid closure, sudden stoppage of flow, and the resulting hydraulic transients. Plug valves are common in process or industrial applications.

Ball valves are used primarily for on-off service and some throttling. They are similar to the plug valve but use a rotating ball with a hole through it. Many garden hose attachments are ball valves, requiring a quarter-turn to open or close, but many faucets are also ball valves that require many turns. Large ball valves are used to throttle flow in pump-discharge lines.

Diaphragm valves handle corrosive, erosive, and dirty service. They close by means of a flexible diaphragm attached to a piston, sometimes called a compressor, that can be lowered by the valve stem onto a weir to seal and cut off flow. Diaphragm valves are used for waste water, industrial fluids, and for mining applications, such as pumping light slurries or tailings-reclaim water.

Pinch valves are particularly suited for slurries or liquids with large amounts of suspended solids. They seal by means of one or more flexible elements, such as a rubber tube, that can be pinched to shut off flow. The flexible element can vary widely from food-grade to special natural and synthetic rubbers to handle corrosive and/or abrasive fluids and mixtures.

Needle valves are volume-control valves that restrict flow in small lines. Needle valves are commonly used for speed control in piloting by allowing operators to set the time required for fluid to move to or from the valve piston chamber. The fluid going through the valve turns 90 degrees and passes through an orifice that is the seat for a rod with a cone-shaped tip. Positioning the cone in relation to the seat changes the size of the orifice.