A fitting is any part used in a piping system to change direction or function and joined to that system by some mechanical means or by welding. The simplest way to change the direction of a pipe would be to bend it.However, besides restricting the flow, this method often distorts the shape of the pipe and reduces the wall strength. Another method of altering direction is with mitered joints, I.e. straight piecesof pipe cut for the required turn and welded together. This type lowers flow efficiency considerably by creating greater turbulence. A single mitered bend has about six times the resistance of a smooth elbow. Fittings are preferable for most piping systems where rate of flow, internal pressure and protection against a corrosive environment are primary design considerations