This is by far the most common application for Ductile Iron Pipe. Because of its reliability and durability, it is the ideal choice for the transmission and distribution of potable water. The value of potable water is rapidly increasing. Water lost between the treatment plant and the customer’s meter is revenue lost. From the aspect of protecting the public health, it is vitally important to protect water quality from treatment to point of use. With the exception of some special linings for sewer service, virtually all of the products marketed by U.S. Pipe & Foundry are approved by the National Sanitation Foundation (NSF) for the conveyance of potable water.
Historically, the primary purpose for developing a system to distribute water was for fighting fire. The concern for the protection of lives and property was paramount, even above that of providing water for drinking and sanitation. A fire protection system must be absolutely reliable and fully functional at all times. Factory Mutual is an insurance organization with a focus on risk management and the prevention of property loss. In that role, they are particularly interested in fire protection systems, most of which are 12" and smaller. Most of the products 12" and smaller marketed by U.S. Pipe and Foundry are approved by Factory Mutual for use in fire protection systems.
The National Fire Protection Association is a national organization that promulgates codes and standards dedicated to fire safety and prevention. It is common for one such body to recognize and accept standards written by another organization, and to incorporate them into their own. Many of the NFPA Standards for fire protection systems incorporate the same American Water Works Association Standards to which U.S. Pipe and Foundry manufactures its products.
Ductile Iron pipe and fittings are ideally suited for wastewater systems. Wastewater pipelines fall into two categories: gravity sewers and force mains. A leaking sewer line can spread contaminated wastewater to the groundwater system. Infiltration and inflow (I&I) can overburden the wastewater treatment plant, since every gallon flowing to the plant must be treated. Severe I&I also leads to extremely excessive treatment costs. It is important to specify and install a durable piping material with reliable joints. U.S. Pipe’s TYTON JOINT® and TR FLEX® Pipe joints are bottle-tight, preventing both I&I and exfiltration.
In a gravity sewer system, wastewater flows downhill through the force of gravity. Gravity systems generally do not flow full, which can lead to septic sewage transformations that can lead to hydrogen sulfide gas being converted to concentrated sulfuric acid, which is very aggressive toward cement mortar linings and Ductile Iron. In a properly designed and constructed gravity sewer system, there will be adequate slope to provide a self-cleaning velocity (generally accepted as 2 ft/sec.). Under these conditions, a standard cement mortar lining will provide adequate corrosion protection for the pipeline. For less than optimum conditions, PROTECTO 401™, a ceramic epoxy lining, is recommended.
Gravity sewers must often be installed at great depths in order to achieve adequate slope. The inherent strength of Ductile Iron enables it to withstand the external loads imposed by the earth at greater depths. As the gravity sewer increases in depth, it will reach a practical limit. At this point in the project, wastewater is collected at a pumping station. The discharge line from the pump station is then a force main, since the wastewater is pumped under pressure.
A sewer force main operates as a pressure line. It does not have to be installed to a precise grade. For maximum hydraulic efficiency it should flow full at all times. This generally requires air relief valves at all high spots in the pipeline. When the pipe is kept full, there is no opportunity for hydrogen sulfide gas to collect, which virtually eliminates the possibility of septic sewage transformations. A standard cement mortar lining is usually adequate to protect the pipeline. Other linings, such as PROTECTO 401™, are available if the designer so specifies.
A reclaimed water pipeline conveys treated wastewater for beneficial re-use. Only products meeting the requirements for potable water should be specified for reclaimed water, since, ultimately, reclaimed water usually ends up in the potable water supply system.
Digester Gas - Not!
Ductile Iron pipe and fittings are not suitable for digester gas service; thus, U.S. Pipe will not knowingly supply products for such a project. At one time, the ANSI A21.52 and A21.14 standards governed the manufacture of Ductile Iron pipe and fittings (respectively) for gas service. These standards were withdrawn a number of years ago. Ductile Iron pipe for gas service was required to undergo special processing and testing. The equipment needed is no longer available at any U.S. Pipe facilities.