What does a 90-degree street elbow do in plumbing?

A 90-degree street elbow is designed specifically to connect two sections of pipe at a right angle, facilitating the change in direction within a plumbing system. The unique construction of a street elbow allows one end to fit inside a pipe while the other end connects to the outside of another pipe, which is particularly useful in tight spaces or where a less bulky connection is needed. This makes it ideal for navigating corners or bends in piping layouts, ensuring a smooth transition for the flow of water or other substances through the system.

The other options pertain to functions that do not describe the specific purpose of a 90-degree street elbow. For instance, creating a seal between pipes is typically associated with fittings like threaded or compression fittings rather than a street elbow. Similarly, while it's important for plumbing components to facilitate flow, a street elbow does not inherently reduce water flow; rather, it directs it. Lastly, vertical support is more closely related to brackets or hangers designed to stabilize pipes, which is outside the functional scope of a street elbow.