The strength, durability, and long service life of Ductile Iron Pipe's predecessor, gray Cast Iron pipe, are widely recognized. The first official record of Cast Iron pipe installation was in 1455 in Siegerland, Germany. In 1664, French King Louis XIV ordered the construction of a Cast Iron pipe main extending 15 miles from a pumping station at Marly-on-Seine to Versailles to supply water to the fountains and town. This pipe served the palace gardens for more than 330 years. Cast Iron pipe was introduced to the United States as early as 1817, when it was installed in the Philadelphia water system. Today, more than 600 utilities (in the United States and Canada) have had Cast Iron mains in continuous service for more than 100 years. Additionally, at least 21 utilities have had Cast Iron mains in continuous service for more than 150 years. Ductile Iron not only retains all of Cast Iron's attractive qualities, such as machinability and corrosion resistance, but also provides additional strength, toughness, and ductility. It is lighter, stronger, more durable and more cost effective than Cast Iron.
Although its chemical properties are similar to those of Cast Iron, Ductile Iron incorporates significant casting refinements, additional metallurgical processes, and superior quality control. Ductile Iron Pipe's improved qualities are derived from an improved manufacturing process that changes the character of the graphite content of the iron. Its graphite form is spheroidal, or nodular, instead of the flake form found in Cast Iron. This change in graphite form is accomplished by adding an inoculant, usually magnesium, to molten iron of appropriate composition during manufacture.
Ductile's high degree of dependability is primarily due to its high strength, durability, and impact and corrosion resistance. Ductile Iron has minimum strength requirements of 60,000 psi tensile strength, 42,000 psi yield strength, and 10 percent minimum elongation. Designed and manufactured to the industry's most stringent standards, Ductile Iron Pipe resists damage during shipping and handling, and, once installed, withstands the most demanding operating conditions, including water hammer, frozen ground, deep trenches, areas of high water table and heavy traffic, river crossings, pipe on supports, rocky trenches, and areas of shifting, expansive, and unstable soils. Additionally, numerous laboratory and field tests have proven that Ductile Iron's corrosion resistance is equal to or greater than that of Cast Iron, which has a service history that is unequaled by any other piping material.