Tee-wyes are similar to tees, except for angling the branch line to reduce friction and turbulence. They are commonly used to attach a vertical drainpipe to a horizontal one, reducing the deposition of entrained solids at the junction. Wyes and combo wyes follow a long-sweep pattern relative to sanitary tees and other short-sweep bends, which have a smaller radius and require less space. 
Wyes also have industrial applications. Although low-priced wyes are often spot-welded, industrial-strength wyes are flash-welded at each seam. In long-distance pipeline applications, a specialized wye is used to allow insertion of pigging to keep pipes clear and flowing.