In addition to elbows, carbon steel pipe fittings also include tees, which connect 3 sections of pipe, producing joints for fluid flow. Equal tees are utilized when the attaching branches are of the same diameter, while reducing tees are utilized when the branch pipe is of a smaller sized size. https://ziegler-fog.technetbloggers.de/maximizing-efficiency-with-carbon-steel-elbows-a-comprehensive-guide