One 3" 90-degree elbow has the same resistance as what length of 3" pipe?

The resistance to flow caused by a fitting such as a 90-degree elbow can be expressed as an equivalent length of straight pipe. In this context, a 3-inch 90-degree elbow is equivalent to a certain length of 3-inch pipe due to the turbulence and restriction it creates as fluid flows through it.

Industry calculations provide a standard equivalence for fittings like elbows. For a 3-inch 90-degree elbow, the equivalent length of straight pipe is typically found to be around 5 feet. This means that when using this elbow in a system, the resistance it adds can be considered equal to that of 5 feet of straight 3-inch pipe.

This approach is used in HVAC and plumbing to simplify the calculation of pressure losses in a system, allowing technicians to estimate how much additional resistance is introduced by various fittings and bends. Hence, knowing that a 3-inch 90-degree elbow is approximately equivalent to 5 feet of straight pipe helps in designing and analyzing the efficiency of a heating or cooling system.