Flow CapacityThe primary purpose of a water line is to deliver water. Size determination hinges on that point. Although variation in the ability of different pipes to deliver water should be considered, S T E E L pipe is a product of great adaptability. The standards embrace many sizes and wall thicknesses; there are hundreds of standard fittings and accessories. As a material, steel can be rolled, formed, welded, forged or cast. The shapes that steel may be made to take are infinite in number, which means that any common requirement can be met; but the proper selection of what to use in a given case, under given operating conditions, becomes a matter of judgment and engineering design.Manufacturers and users of steel pipe for water service have had much experience in this matter of application, and have contributed to the solution of common and special problems.The aim of this paper is to gather and present general engineering data and references bearing on the more common problems met in the design of steel water lines.