1- what Schedule CI pipe are you talking about?
Extra heavy, Standard Or no Hub?
Is this cast Iron coated or un coated?
What is the average ambient temperature these pipes are located?
What is the pH of the rain as the huge fires that were caused during the Gulf war could have put an excessive amount of sulfur into the atmosphere.
What country did this cast Iron come from and made under which standards?
A lot of times CI will crack on the top when not used very often.