Availability of Materials
Q: I have reviewed the ASTM and CISPI standards and cannot find a special fitting which I need. Does this mean that it is no longer available?
A: The ASTM and CISPI standards include all of the most popular fittings; however additional fittings not found in the standards may be available. Don’t give up until you have checked with the manufacturers. Email The Institute if you need help, or contact a specific foundry directly.
Q: Occasionally a representative will suggest that I specify a particular type of coupling in my specification by brand name. Is there a generic standard that I can reference for the different types of couplings that will identify the different types of couplings without naming a specific manufacturer?
A: There are three standards for couplings referenced in each of the model plumbing codes; they are as follows:
CISPI 310 – This standard covers stainless steel shielded couplings with a rubber (ASTM C564) gasket sleeve. These couplings are the most widely used, and have been produced since the early 1960’s. We estimate that 1.5 billion have now been installed. These couplings are produced by numerous manufacturers and are sold by all of the cast iron soil pipe and fittings manufacturers.
ASTM C1277 – This standard covers stainless steel and cast iron shielded couplings with a rubber (ASTM C564) gasket sleeve. This standard, which was completed a couple of years ago, covers all types of shielded couplings.
ASTM C1173 – this standard covers transition couplings used to join different types of piping materials in underground installations. The couplings can be shielded or unshielded, and the gasket material is not required to meet a specific standard. A standard is, however, currently being developed for the gasket material through ASTM, but it has not yet been completed. An ASTM subcommittee has also begun work on a standard to cover shielded transition couplings for use above and below ground, but this standard has not been completed.
Q: When using hub and spigot pipe with rubber compression gaskets or hubless pipe with stainless steel and rubber couplings, is there a maximum allowable joint deflection recommended?
A: The Cast Iron Soil Pipe Institute and its members recommend a five-degree maximum deflection limit. This assures a good tight joint. For more than five degrees of deflection, fittings should be used.
Differences in Types of Iron
Q: The water works representatives tell me that cast iron pipe is no longer manufactured for water service, and I need to specify ductile iron pipe. What is the difference?
A: Cast iron is a commonly used term to describe many types of iron. The word “cast” simply identifies the method used to produce the finished product, and not to describe the material itself. The casting method involves pouring the iron in a molten or liquid form into a mold which defines the shape of the finished product. Irons are also sometimes identified by color or physical properties. The most common iron is gray iron (the color of the iron once it has cooled). Cast iron soil pipe and fittings are produced from this type of iron. Cast iron tubs, drains, many iron body valves, fire hydrants, automotive engine blocks, brake drums, manhole covers and wrecking balls are also made of this type of iron. Ductile iron is a form of cast iron in which the addition of magnesium to the gray iron mixture in its molten state reforms the graphite flakes (which occur in gray iron) into nodular shapes. While it is true that “gray” cast iron water pipe is no longer manufactured, ductile iron is still a type of cast iron. For more information on ductile iron visit DIPRA (Ductile Iron Pipe Research Association), or review The Urban Conservation Glossary, by Neil Grieve.
Hanging and Support
Q: Does cast iron pipe require special support or hanging?
A: Cast iron pipe and fittings is simple to properly hang and support. There are a few basic rules:
- A hanger should be located within 18 inches of each coupling or hub for lengths up to 10 feet.
- For multiple joints within a four-foot length, a hanger should be located at alternate couplings or hubs.
- Support should be provided at each floor for vertical stacks.
For more information on hanging, seismic and sway bracing see General Installation Instructions in Chapter 4 of the Cast Iron Soil Pipe and Fittings Handbook.
Q: We are working on a remodel of a 40 year old building and have been asked to make a recommendation on the condition of the cast iron soil pipe and fittings. What is the life expectancy of cast iron soil pipe and fittings?
A: The oldest installations of cast iron pipe are in underground lines, both water and gas. Many are over 100 years old, and some date back 200 – 400 years and are still in use. Many older buildings with cast iron installed inside are approaching the 100 year mark. We would suggest a good physical examination of any exposed piping and removal of a section to examine the interior for possible signs of corrosion. If the wall thickness of the pipe still falls within the specified dimensions, the pipe need not be replaced. It is important to note that the wall thickness on the older piping may not and need not be uniform. Centrifugal casting of pipe began roughly 35 years ago and results in a very uniform wall thickness. The pipe produced before centrifugal casting was statically cast – a process which produced pipe with some differences in wall thickness. This variable wall thickness should not be a concern as long as the thinnest wall thickness is equal to or greater than the specified minimum thickness. Contact the CISPI representative in your area to get advice on proper methods of measuring wall thickness and the minimum wall thickness required by the specific standard.
Q: What is the maximum temperature for cast iron soil pipe and fittings?
A: The limiting factor in the operating temperature range for cast iron soil pipe and fittings is the gasket material. ASTM C564 gasket materials can be safely used up to 212°F. If a special situation requires an operating temperature above this limit, special gaskets can be used, but these are costly and not readily available. It is always wise to check with the pipe and fittings manufacturers before specifying a special gasket.
Q: I sometimes see cartoons in advertisements for hubless couplings and the couplings are shown leaking. Does this really happen and what would cause a coupling to leak?
A: Properly installed hubless couplings do not leak or fail. Hubless couplings used to join hubless pipe and fittings together utilize a rubber gasket sleeve which is compressed by a stainless steel shield and clamp assembly. On the few occasions in which leaks have occurred, the leaks were caused by movement in the joint and resulting partial separation. These movements are usually caused during tests when installers attempt to test multiple floors without proper thrust restraint. Thrust occurs when a column of water fills a vertical stack. A 10-foot column of water (recommended for testing purposes) produces pressure of 4.3 PSI at the base of the column, but thrust increases as the diameter of the column of water increases. A four-inch stack with 10 feet of hydrostatic head produces 65 pounds of thrust at the base of the stack: a 10-inch stack with the same ten feet of hydrostatic head produces 337 pounds of thrust even though the pressure in both stacks is only 4.3 PSI. This thrust pushes against the pipe and fittings at the base of the stack where the vertical line turns horizontal. This force, if the piping is not properly restrained, can cause the joint to move, which could result in partial joint separation, and leaks (especially in large diameter pipe and fittings). For information on blocking or thrust restraint contact us for a copy of our installation instructions.
Q: Can I use hubless cast iron soil pipe and fittings below ground, and is there anything special I need to do to protect the couplings?
A: Hubless cast iron soil pipe and fittings are allowed for underground installations by all of the model codes. Since the 300 series of nickel chromium stainless steel is even more resistant to corrosion than cast iron, the stainless steel hubless couplings used to join hubless cast iron soil pipe require no more special protection against corrosion than the pipe itself. Even though all of the model codes allow hubless pipe and fittings below ground, a few local jurisdictions have local amendments which require that only hub and spigot be used underground. It is always best to check local amendments. For a more thorough discussion of underground installation procedures see Chapter 4 of the Cast Iron Soil Pipe and Fittings Handbook.