Water Transmission

Northwest Pipe Company is the largest provider of steel water pipe in North America, manufacturing spirally welded pipe, rolled-and-welded straight seam pipe, and custom fabricated pipe and fittings for the water market in diameters of 24-inch through 156-inch.

water_transmission_overviewPotable Water Systems – A conveyance portion of a potable water system consists of Transmission mains, and a network of Distribution mains. Raw water, whether it is drawn from surface or ground supplies, must first be conveyed to a community, then distributed to consumers.

Conveyance from the source to the point of treatment is typically provided by larger diameter pipelines, called transmission mains, typically at least 24-inch in diameter. Following treatment, transmission mains also carry the potable water to the distribution pipeline network for delivery to homes and businesses.

Transmission lines contain few interconnections, while the distribution system is a complex network of loops and interconnecting pipes of small diameters, typically no larger than 12-inch. Today, steel water pipe, manufactured to AWWA C200, is one of the most widely used pipe materials for water transmission in North America.

History of Steel Water Pipe in North America – Steel pipes have been in use for more than 150 years in the United States, with the first known and recorded installation taking place in 1858 in Railroad Flat, California. This water pipe was made of riveted steel and diameters ranged from 11-inch to 22-inch, with a wall thickness of 16 gage. The pipe continued to stay in service more than a hundred years later, into the 1970’s. In 1926, one of the first welded steel lines, 80 miles long and ranging in diameters of 61-inch to 65-inch, was installed on the Mokelumne Aqueduct of the East Bay Municipal Utility District, California.

It is estimated that by 1940, there was approximately 3,500 miles of steel water pipe in the ground around the United States. By the 1970’s there was some 5500 miles of steel pipe in service. Since the 1940’s, the large diameter water transmission mains market has primarily been served by spiral welded steel pipes, steel-cylinder type composite concrete pressure pipes, and to a lesser extent, by ductile iron pipes.

Composite concrete pressure pipes first appeared on the market out of necessity during WWII due to steel shortages. At the height of its popularity in the 1970’s, there were six major manufacturers of PCCP in the US, with at least twenty-two plants scattered throughout the country; today there are three PCCP manufactures in the US, with a total of six plants.

For large diameter water transmission applications, steel pipe is most widely specified today, with two of the three PCCP manufacturers in the US also manufacturing steel pipe. Northwest Pipe Company is the largest of four major steel pipe manufacturers with plants located nationwide that supply steel water transmission pipe, fittings and other specials.

Serving the Needs of Critical Water Transmission Projects – Some of the largest water transmission projects in the United States are being built with spiral welded steel pipelines. The Integrated Pipeline (IPL) project is 148 miles in length with pipe diameters of 108-inch, and is being built in North Texas to bring water from Lake Palestine to Tarrant Regional Water District and the Dallas Water Utilities. The Provo Reservoir Canal Enclosure Project was a 21-mile long, 126-inch diameter pipeline, with polyurethane lining and coating, built to enclose a canal and prevent an annual loss of 2.6 billion gallons of water. Stake holders included the US Bureau of Reclamation, Metropolitan Water District of Salt Lake & Sandy, Jordan Valley Water Conservancy District, and the Central Utah Water Conservancy District. Construction was recently completed on the 45-mile long, 66-inch diameter, Southern Delivery System in Colorado. The purpose of the project is to convey raw water from the Arkansas River stored in the Pueblo Reservoir to the City of Colorado Springs, the City of Fountain, Security Water District, and Pueblo West Metropolitan District.

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