Longitudinal cracking in cast iron pipe
I work in maintenance at a commercial building in Michigan. We have a 5 story parking structure with 3" & 4" cast iron pipe routing drain water from vehicles and rain/snow into a lift station. The building is approximately 15 years old. The past 3-4 years I have replaced on average about 100 feet of pipe a year. It cracks end to end, usually on the bottom (but not always). The cracks are not caused by freezing water in a clogged pipe. There is always some residue in the bottom of the pipe, but it is not clogged. I can only assume it is caused by salt from the vehicles being trapped in the residue and eating through the pipe. What I want to know is, is this common, or did the contractors use sub-standard pipe in the construction? I have pursued the idea of replacing the broken pipe with PVC or ABS, but was told it has to be cast iron by local building code. Thanks for any insight you might have.