Northwest Pipe goes with the flow. The company makes welded-steel water transmission lines that form the circulatory systems of water suppliers. Its transmission pipes -- some large enough to walk through -- are made to transport water under pressure and sold primarily to public water utilities in the US and Canada. Northwest Pipe also manufactures tubular products from 1.5 inches to 16 inches in diameter for the construction, agriculture, and energy markets. The company's Water Transmission division has manufacturing facilities in six US states and in Mexico, and its Tubular Products unit has manufacturing sites in three US locations. Northwest Pipe Asia, in Singapore, produces steel pipe mills.