Cast Iron Soil Pipe & Fittings Handbook
Chapter 1 - Cast Iron Soil Pipe History, Uses and Performance
Cast Iron Soil Pipe Joints and Their CharacteristicsThe cast iron soil pipe gasketed joints shown in Figure 1 are semi-rigid, water tight connections of two or more pieces of pipe or fittings in a sanitary waste, vent, or sewer system. These joints are designed to give rigidity under normal conditions and still permit sufficient flexibility under adverse conditions, such as ground shift, footing settlement, wall creepage, building sway, etc., to allow pipe movement without breakage or joint leakage. Properly installed, the joints have equal longevity with the cast iron soil pipe, and can be installed in walls, under ground, and in other inaccessible places and forgotten.
Types of Cast Iron Soil Pipe and FittingsCast Iron Soil Pipe used in the United States is classified into two major types - hub & spigot and hubless (No Hub).
Hubless cast iron soil pipe and fittings are simply pipe and fittings manufactured, without a hub, in accordance with ASTM A888 or CISPI 301. The method of joining these pipe and fittings utilizes a hubless coupling which slips over the plain ends of the pipe and fittings and is tightened to seal it. Hubless cast iron soil pipe and fittings are made in only one class or thickness. There are many varied configurations of fittings and both pipe and fittings range in sizes from 1 1/2" to 10". Couplings for use in joining hubless pipe and fittings are also available in these same size ranges from the member companies of the Cast Iron Soil Pipe Institute.
Hub and Spigot pipe and fittings have hubs into which the spigot (plain end) of the pipe or fitting is inserted. The joint is sealed with a rubber compression gasket or molten lead and oakum. Hub and Spigot pipe and fittings are available in two classes or thicknesses. These are classified as Service (SV) and Extra Heavy (XH). Because the additional wall thickness is added to the outside diameter Service (SV) and Extra Heavy (XH) have different outside diameters and are not readily interchangeable. These two different types of pipe and fittings can be connected with adaptors available form the manufacturer. Hub and Spigot pipe and fittings are made in accordance with ASTM A-74 and are available in 2"-15" sizes. Compression gaskets, lubricant, and assembly tools are available from the member companies of the Cast Iron Soil Pipe Institute.
Shielded Hubless CouplingThe shielded hubless coupling for cast iron soil pipe and fittings is a plumbing concept that provides a more compact arrangement without sacrificing the quality and permanence of cast iron. The illustrated design in Figure 1 shows the system typically uses a one-piece neoprene gasket, a shield of stainless steel retaining clamps. The great advantage of the system is that it permits joints to be made in limited-access areas.
The 300 series stainless steel, which is often used with hubless couplings, was selected because of its superior corrosion resistance. It is resistant to oxidation, warping and deformation, offers rigidity under tension with a substantial tensile strength, and yet provides sufficient flexibility.
In the illustration below, the shield is corrugated in order to grip the gasket sleeve and give maximum compression distribution. The stainless steel worm gear clamps compress the neoprene gasket to seal the joint. The gasket absorbs shock, vibration and completely eliminates galvanic action between the cast iron soil pipe and the stainless steel shield.
(A) Typical Hubless Coupling
(B) The Compression Joint
(C) The Lead and Oakum Joint
The Compression JointThe compression joint is the result of research and development to provide an efficient, lower-cost method for joining cast iron soil pipe and fittings. The joint is not unique in application to cast iron soil pipe, since similar compression-type gaskets have been successfully used in pressure pipe joints for years. As shown in Figure 1, (B) the compression joint uses hub and spigot pipe as does the lead and oakum joint. The major difference is the one-piece rubber gasket.
When the spigot end of the pipe or fitting is pushed, or drawn, into the gasketed hub, the gasket displaces and compresses to seal the joint. The resulting joint is leak-proof and root-proof. It absorbs vibration and can be deflected up to 5 degrees without leakage or failure.
The Lead and Oakum JointCast iron soil pipe joints made with oakum fiber and molten lead are leak-proof, strong, flexible and root-proof. The waterproofing characteristics of oakum fiber have long been recognized by the plumbing trades, and when molten lead is poured over the oakum in a cast iron soil pipe joint, it completely seals and locks the joint. This is due to the fact that the hot metal fills a groove in the bell end of the pipe, firmly anchoring the lead in place after cooling. When the lead has cooled sufficiently, it is caulked into the joint with a caulking tool to form a solid metal insert. The result is a lock-tight soil pipe joint with excellent flexural characteristics.
Soundproofing Qualities of Cast Iron with Rubber Gasket JointsOne of the most significant features of the compression gasketed joint and hubless couplings is that they assure a quieter plumbing drainage system. The problem of noise is particularly acute in multiple dwelling units. Although soundproofing has become a major concern in construction design, certain plumbing products have been introduced which not only transmit noise but in some cases actually amplify it. The use of neoprene gaskets and cast iron soil pipe reduces noise and vibration to an absolute minimum. Because of the density and wall thickness of the pipe, sound is muffled rather than transmitted or amplified, and the neoprene gaskets separate the lengths of pipe and the units of fittings so that they suppress any contact-related sound. The result is that objectionable plumbing noises are minimized.
A detailed discussion of the soundproofing qualities of cast iron soil pipe DWV systems is contained in Chapter X.