Cause of Cracked cast iron

[carpentermatt]

I am a general contractor in Chicago and recently completed a job that involved tying into the existing cast iron sewer main. My licensed plumber installed a vertical piece of PVC into a horizontal piece of cast iron. after that point the cast runs for about 4'0" and continues through the foundation into the village sewer. The connection is located in a crawl space, that has decent but not great heat at the location of the pvc/cast joint. The plumbing work was completed in middle to late february. I am not sure when the crack occured but as of May 1st the homeowner has called and told me that there is a crack, large enough to fit a screwdriver into, in the cast running the from the pvc connection into the foundation wall. The homeowner feels that the crack was caused by the fact that there is nothing supporting the area from the pvc/cast connection to about half way to the foundation. There is not much weight on top of the cast at all the pvc runs vertical for aprox. 3'-0" and then 90's to a horizontal run, which at that point the pvc pipe is supported. Does anyone have any idea why the cast may have cracked? I find it hard to believe a crack that large was caused due to the lack of support at the connection area.

[HayZee518]

I'm thinking that the crack may have occured at a hub - you know the joints in cast are hub and spigot. if the cast isn't supported from underneath on sand it could crack from the shear weight of it. if the plumber made a splice with pvc and furnco couplings there wouldn't be any appreciable weight there.

[jnaas2]

Can you get a picture ?

[carpentermatt]

I will have pics. in the morning. However, it is to my understanding that the crack runs down the pipe from the hub to the foundation wall.

[Redwood]

How old is this cast iron and is it service weight, no hub, or extra heavy?
Pictures would help!