Joint Integrity
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After ruling out internal spikes in pressure (also known as waterhammers), pipe corrosion, differential settlement, surface loading, cathodic exposure, thermal expansion/contraction, and numerous other prospective causes of pipe failure, the engineering study discovered that the sulfur based joint sealant (noted in pink) that was standard for pipes built in the 1930s 40s was reacting with water in the soils and with the cast iron pipe which created expansion pressure in the joints. When this joint swelling pressure exceeded the threshold of the cast iron pipes to flex, it caused the pipe to blow-apart as the cast iron snapped under extreme joint pressures. |
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This joint problem was subsequently confirmed in research studies from other cities around the country that used the same joint compound as Kingsport. The use of this compound ended in the early 1950s based on the failure of many of the newly installed pipes. If there is any good news, it is that the pipes in Kingsport lasted much longer than most communities that used this product. |