Stop valves are used in plumbing to either halt or control the flow of water through a pipe. Stop valves come in a wide variety of different types, all of which are useful in their own way. Before embarking upon a plumbing project, it is a good idea to familiarise yourself with these different types and where and how to best use them.
Globe valves are the most common type of stop valves. Globe valves are named for their globular shape. Ultimately, the only way to truly identify a globe valve is to look at it internally. Globe valves can come in straight-flow, angle-flow and cross-flow models. Straight-flow globe valves simply stop water flow from achieving forward progress; angle-flow valves direct the flow in a certain direction; cross-flow valves allow an additional flow of water to join a flow already headed in a straight line. Globe valves are most often used with oil and gas.
Gate valves are only used when there is a straight flow of water, gas or oil. Two types of gate valves exist: rising stem and non-rising stem. The difference between the two is self-explanatory: rising stem gate valves have stems that move along with the valve's gate as the hand wheel is turned. On non-rising stem gate valves, the stem stays in one place while the gate moves up and down.
Butterfly valves are characterised by their butterfly disks, which, when even with the sides of the pip, stop flow, but allow more and more flow the farther they are rotated. Butterfly valves require little space and little pressure loss. They are usually designed to be rotated no more than 60 degrees, but some high-performance models can be rotated as much as 90 degrees.
Ball valves consist of a ball embedded in the pipe that acts as the primary agent to control flow. The ball has a hole through it so that when the ball is rotated more and more fluid is allowed through the hole. You only need to rotate ball valves 90 degrees to completely open or close the valve.