AMERICAN Ductile Iron Pipe

Summary of Standards

for Ductile Iron Pipe and Ductile Iron Fittings

Most of the standards covering pipe and fittings manufactured by AMERICAN Cast Iron Pipe Company have been prepared by the American Water Works Association Standards Committee A21. Other applicable standards generally cover specialties or refer to ANSI standards.

To take advantage of modern metallurgical science, better testing methods, improved production control, materials with better physical properties, and improvements in manufacturing methods, the A21 Committee has a continuing program to keep its standards revised to include the latest developments.

Development of Standards

The AWWA Standards Committee A21 on Ductile and Gray Iron Pipe and Fittings was organized in 1926 under the procedures of the American Engineering Standards Committee. It was reorganized under American Standards Association Procedures in 1955, and in 1984 it became a member of the AWWA committee structure.

The committee is responsible for the development of standards and manuals for ductile iron pressure pipe for water and other liquids and for fittings used with such pipe. The committee’s membership is comprised of representatives from consumer groups, producer groups and general interest groups, including a number of professionals from AMERICAN.

A standard, manual or revision is developed by a subcommittee assigned to that task. The subcommittee prepares and submits the document to the Standards Committee for approval. After approval it is submitted to the AWWA Standards Council for approval. After all approvals have been received, including a public review by both AWWA and ANSI, the standard, manual or revision is published and made available to the public.

Abbreviations of Organizations

The following is a list of the organizations referred to in this and other sections of this website by abbreviation:

AASHTO American Association of State Highway and Transportation Officials
ACI Alloy Casting Institute
AISI American Iron and Steel Institute
ANSI American National Standards Institute
API American Petroleum Institute
ASCE American Society of Civil Engineers
ASME American Society of Mechanical Engineers
ASTM American Society for Testing and Materials
AWWA American Water Works Association
BSI British Standards Institute
DIPRA Ductile Iron Pipe Research Association
DIS Ductile Iron Society
FM FM Global
ISO International Organization for Standardization
MIL United States Military
NEWWA New England Water Works Association
NSF NSF International
UL Underwriters Laboratories
WEF Water Environment Federation

Specification History

A brief review of the older specifications in chronological order may help define their usefulness, as well as help in the appreciation of the improved modern standards.

The basis for design in almost all specifications to date is the Barlow formula, or "Hoop Stress" formula. It embodies the basic principle for design of a cylinder for internal pressure. The formula may be stated as t= PD/2S in which t is the thickness of the pipe in inches; P is the internal pressure in pounds per square inch (psi); D is the outside diameter in inches; and S is the allowable working stress of the metal in pounds per square inch.

In the development of the design of cast iron pipe, this formula has been modified in several ways by prominent water works engineers such as Allen Hazen, Thomas H. Wiggin, James T. Fanning, Dexter Brackett, I. J. Fairchild and James P. Kirkwood. Mr. Kirkwood, as chief engineer for the Brooklyn Water Works, developed a design for cast iron pipe that was a variant of the Barlow formula. Kirkwood’s calculations took into consideration casting imperfection, strength of the metal and other factors affecting the life of the pipe. In the late 1880s, a formula by Dexter Brackett, distribution engineer for the City of Boston, was adopted by the New England Water Works Association as its standard.

Although the 1902 NEWWA standards did not provide a formula for pipe thicknesses, the Brackett formula was used in determining the thicknesses recommended.

In 1908, AWWA adopted a standard covering bell and spigot pipe produced in 12-foot laying lengths by the pit casting method. Prior to 1908, at least two unofficial documents dealing with pipe design were acknowledged by AWWA. The first of these used thicknesses for pipe determined by averaging the thicknesses used in a large number of American cities. The second dealt with actual design of pipe based on Brackett’s method with variations.

The 1908 AWWA standards employed a system of class designations applied to specific wall thicknesses in diameters 4" to 84" inclusive for a range of hydraulic heads. The most common of these classes were A, B, C and D for 100, 200, 300 and 400 feet hydraulic head, respectively. The design was based on a variation of the Brackett formula by J. T. Fanning and included a variation in the outside diameter for the different classes of pipe. The basic design of pipe with a different outside diameter for each class was followed in modern specifications until the 1961 revisions. The general acceptance by the water works industry of the standardized mechanical joint necessitated a universal outside diameter for cast iron pipe.

AWWA revised its standards in 1939 to incorporate a new method of designing cast iron pressure pipe. This new method was published as ANSI A21.1. The A21.1 method of determining the required thickness of cast iron pipe took into consideration trench load and internal pressure in combination. Trench load consists of the earth load on the pipe plus any transient load resulting from traffic over the trench; internal pressure consists of the design working pressure plus an additional allowance for surge pressure. Laying conditions and properties of the iron in the pipe are also factors involved in the design. Additions for casting tolerance are included in the design thickness. With the advent of ductile iron pipe and its flexibility, this additive method of design became obsolete. As noted in the following paragraph, ductile iron design employs flexible conduit principles since the internal pressure relieves the external load.

Actually, the first standard covering centrifugally cast pipe was issued by the U.S. government in 1927, and was known as  Federal Specification No. 537. In July 1931, the specification was revised to include pipe cast centrifugally in sand-lined molds, pipe cast centrifugally in metal molds and pit cast pipe. This specification has been modified several times and is now basically the same as ANSI/AWWA Standards.

Development of ductile iron in the 1950s initiated research into design of ductile iron pipe to take advantage of the superior flexibility, strength, toughness, impact resistance and corrosion resistance of this new metal. The A21 Committee issued the ANSI A21.50 (AWWA H3-65) and ANSI A21.51 (AWWA C151) Standards for ductile iron pipe in 1965. The work of M. G. Spangler and others at Iowa State University on flexible conduit is the basis for principles that have been applied extensively by the designers of flexible underground pipe. The design principles and procedures for ductile iron pipe that were included in the ANSI Standard A21.50 (AWWA C150) were verified by trench tests at AMERICAN and tests conducted by various researchers. AMERICAN’s former Technical Director Dr. Ed Sears was instrumental in these developments.

Continued research on ductile iron pipe reflects through these updated standards the advancements in metallurgical technology and manufacturing skills. Furthermore, the quality of AMERICAN’s products and conformance to appropriate specifications are assured by the British Standards Institute’s certification that AMERICAN’s quality system complies with ISO 9001 Quality Management System Standard.

AMERICAN also subscribes to NSF’s listing program for products under ANSI/NSF Standard 61 — Drinking Water System Components — Health Effects. Check with AMERICAN for current listing of our products.

Standards Applicable to AMERICAN Pipe and Fittings

Throughout this website, Standards may be referred to as listed below or by only the ANSI, AWWA, ASTM, NSF, ASME, etc. numbering.

Ductile Iron Pipe for Water and Other Liquids Standards
4" - 64" ANSI/AWWA C150/A21.50
ANSI/AWWA C151/A21.51
Ductile Iron Gravity Sewer Pipe Standards
4" - 64" ASTM A746
Ductile Iron Culvert Pipe Standards
14" - 64" ASTM A716
Ductile and Gray Iron Fittings for Water and Other Liquids Standards
4" - 48" ANSI/AWWA C110/A21.10
Ductile Iron Compact Fittings Standards
4" - 64" ANSI/AWWA C153/A21.53
Flanged Pipe Standards
4" - 64" ANSI/AWWA C115/A21.15
Coatings and Linings Standards
Asphaltic ANSI/AWWA C110/A21.10
ANSI/AWWA C115/A21.15
ANSI/AWWA C151/A21.51
ANSI/AWWA C153/A21.53
Cement Lining ANSI/AWWA C104/A21.4
Fusion-Bonded Epoxy ANSI/AWWA C116/A21.16
Ceramic Epoxy Lining PROTECTO 401
ASTM A716/A746
Coal Tar Epoxy Lining PROTECTO 401
Polyethylene Encasement ANSI/AWWA C105/A21.5
Joints — Pipe and Fittings Standards
Fastite ANSI/AWWA C111/A21.11
Mechanical ANSI/AWWA C111/A21.11
Flanged ANSI/AWWA C110/A21.10
ANSI/AWWA C115/A21.15
ANSI/AWWA C153/A21.53
Grooved and Shouldered AWWA C606

Other joints shown in this section are AMERICAN design.

All Products1 ANSI/NSF Standard 61
NOTE: Many AMERICAN joints, classes of pipe, fittings and specials are listed by Underwriters Laboratories Inc. and FM Global. The quality of AMERICAN’s products and conformance to appropriate specifications are assured by the British Standards Institute’s certification that AMERICAN’s quality system complies with ISO 9001 Quality Management System Standard.

Standards for the Design, Manufacture, Installation and Certification of Ductile Iron Pipe and Ductile Iron Fittings

Standard Designation Subject
ANSI/AWWA C104/A21.4 Cement-Mortar Lining for Ductile-Iron Pipe and Fittings for Water
ANSI/AWWA C105/A21.5 Polyethylene Encasement for Ductile-Iron Pipe Systems
ANSI/AWWA C110/A21.10 Ductile-Iron and Gray-Iron Fittings, 3 in. through 48 in., for Water
ANSI/AWWA C111/A21.11 Rubber-Gasket Joints for Ductile-Iron Pressure Pipe and Fittings
ANSI/AWWA C115/A21.15 Flanged Ductile-Iron Pipe with Ductile-Iron or Gray-Iron Threaded Flanges
ANSI/AWWA C116/A21.16 Protective Fusion-Bonded Epoxy Coatings for the Interior and Exterior Surfaces of Ductile-Iron and Gray-Iron Fittings for Water Supply Service
ANSI/AWWA C150/A21.50 Thickness Design of Ductile-Iron Pipe
ANSI/AWWA C151/A21.51 Ductile-Iron Pipe, Centrifugally Cast for Water
ANSI/AWWA C153/A21.53 Ductile-Iron Compact Fittings, for Water Service
ANSI/AWWA C600 Installation of Ductile-Iron Water Mains and Their Appurtenances
ANSI/AWWA C606 Grooved and Shouldered Joints
ASTM A674 Polyethylene Encasement for Ductile Iron Pipe for Water or Other Liquids
ASTM A716 Ductile Iron Culvert Pipe
ASTM A746 Ductile Iron Gravity Sewer Pipe
ANSI/NSF 61 Drinking Water System Components—Health Effects
ASTM G62 Standard Test Methods for Holiday Detection in Pipeline Coatings

Miscellaneous Standards

The following standards are related to ductile iron and gray iron piping and other products, but are generally not directly applicable to the manufacture of AMERICAN pipe and fittings.

Standard Designation Subject
ANSI A40.5 Threaded Cast-Iron Pipe for Drainage, Vent, and Waste Services
ANSI/ASME B1.1 Unified Inch Screw Threads (UN and UNR Thread Form)
ANSI/ASME B16.1 Cast Iron Pipe Flanges and Flanged Fittings, Class 25, 125, 250 and 800
ANSI/ASME B16.3 Malleable-Iron Threaded Fittings, 150 and 300 lb.
ANSI/ASME B16.4 Cast-Iron Screwed Fittings, 125 and 250 lb.
ANSI/ASME B16.5 Pipe Flanges and Flanged Fittings
ANSI B16.12 Cast Iron Threaded Drainage Fittings
ANSI B16.14 Ferrous Pipe Plugs, Bushings, and Lock-nuts with Pipe Threads
ANSI B16.21 Nonmetallic Flat Gaskets for Pipe Flanges
ASME/ANSI B16.42 Ductile Iron Pipe Flanges and Flanged Fittings
ANSI B18.2.1 Square and Hex Bolts and Screws (Inch Series)
ANSI/ASME B18.2.2 Square and Hex Nuts (Inch Series)
ANSI B31.1 Power Piping
ANSI/ASME B31.8 Gas Transmission and Distribution Piping Systems
ANSI/ASME B1.20.1 General Purpose Pipe Threads
ANSI/AWWA C207 Steel Pipe Flanges for Waterworks Service, 4” through 144”
ANSI/AWWA C500 Gate Valves, 3” through 48” NPS for Water and Sewage Systems
ANSI/AWWA C501 Sluice Gates
ANSI/AWWA C502 Dry-Barrel Fire Hydrants
ANSI/AWWA C503 Wet-Barrel Fire Hydrants
ANSI/AWWA C504 Rubber-Seated Butterfly Valves
ANSI/AWWA C508 Swing-Check Valves for Ordinary Waterworks Service
ANSI/AWWA C509 Resilient-Seated Gate Valves for Water and Sewage Systems
ANSI/AWWA C550 Protective Interior Coatings for Valves and Hydrants
ASTM A48 Gray Iron Castings
ASTM A74 Cast Iron Soil Pipe and Fittings
ASTM A126 Gray Iron Castings for Valves, Flanges, and Pipe Fittings
ASTM A278 Gray Iron Castings for Pressure-Containing Parts for Temperatures Up to 650°F (345°C)
ASTM A319 Gray Iron Castings for Elevated Temperatures for Non-Pressure Containing Parts
ASTM A377 Standard Index of Specifications for Ductile Iron Pressure Pipe
ASTM A395 Ferritic Ductile Iron Pressure Retaining Castings for Use at Elevated Temperatures
ASTM A438 Transverse Testing of Gray Cast Iron
ASTM A476 Ductile Iron Castings for Paper Mill Dryer Rolls
ASTM A518 Corrosion-Resistant High-Silicon Iron Castings
ASTM A536 Ductile Iron Castings
ASTM A571 Austenitic Ductile Iron Castings for Pressure Containing Parts Suitable for Low-Temperature Service
ASTM C150 Portland Cement
ASTM D1248 Polyethylene Plastic Molding and Extrusion Materials
ASTM E8 Tension Testing of Metallic Materials
AASHTO M64 Cast Iron Culvert Pipe
AASHTO M105 Gray Iron Castings
AWWA D100 AWWA Standard for Welded Steel Tanks for Water Storage