Cast Iron Soil Pipe & Fittings Handbook
Chapter 2 - Installation of Cast Iron Soil Pipe and Fittings
Joining Methods for Cast Iron Soil Pipe
Compression GasketsThere are generally three methods used for joining cast iron soil pipe. Hub and spigot cast iron soil pipe may be joined by the compression gasket or a caulked joint. Hubless cast iron soil pipe are joined by using a hubless coupling.
compression gasket is a precision molded one-piece gasket that is made
of an elastomer that meets the requirements of ASTM C-564. The physical
characteristics of this elastomer ensures that the gasket will not decay
or deteriorate from contact with the materials flowing in the pipe or chemicals
in the soil or air around the pipe. The compression joint is made as follows:
Hubless cast iron soil pipe is joined by using the hubless coupling. Several different types of hubless couplings are available. The following will outline the installation procedures of hubless couplings that meet the requirements of CISPI 310. It must be noted that these installation procedures are not intended to be applicable for couplings other than those manufactured in accordance with CISPI 310. These couplings are manufactured using a stainless steel shield and clamp assembly and an elastomeric sealing sleeve conforming to the requirements of ASTM C-564. The following steps should be taken to ensure a proper joint.
Caulked JointsPrior to the late 1950's, the caulked joint was the only method of joining hub and spigot cast iron soil pipe. To make a caulked joint the following steps are used:
Lead and Oakum Required to Caulk Cast Iron Soil Pipe JointsOakum is made from a vegetable fiber and used for packing hub and spigot joints. Cotton and hemp can also be used. These materials are usually twisted loosely into strands or braided and formed into a circular or rectangular cross section. A rough rule-of-thumb method for estimating oakum requirements is to take 10 percent of the weight of the lead required for caulking. Table 5 provides a more accurate method for estimating oakum requirements.
Lead quantities can be roughly estimated by rule-of-thumb as 12 ounces per inch of diameter as a minimum. Thus a 4 inch diameter pipe would require 3 pounds of lead as a minimum. An 8 inch diameter pipe would require 6 pounds of lead. This allows for skimming-off and for a reasonable loss due to spillage in pouring. Table 6 lists suggested lead quantities for various pipe and fitting diameters. The amounts shown apply only to cast iron soil pipe and fittings made according to ASTM Standard A-74.
The standards of the Lead Industries Association contain the specification for lead quality. Lead for caulking purposes should contain not less than 99.73 percent of lead and no more than the following maximum allowable impurities: .08 percent copper, .002 percent zinc, .002 percent iron, .25 per cent bismuth, .02 percent silver, and a total of not more than 0.15 percent arsenic, antimony and tin. The melting point for caulking lead is 621 degrees F, and the proper pouring temperature is 790 - 830 degrees F. The lead is ready for pouring when it becomes a cherry red. After cooling, there is a shrinkage of approximately 5.8 percent from the liquid state.
NOTE: The caulked joint is a very time consuming method of joining cast iron soil pipe. The vast majority of all hub and spigot cast iron soil pipe installed today is joined by using the compression gasket.