Re: cracking pvc trap
I'd have to agree with the others, as I've never experienced any cracking or problems with pvc/abs traps and parts with a disposal or cast waste line in the wall, even with a cheapy flexy stainless sink.
If this is an ongoing problem, get rid of the disposal. With no disposal, you shouldn't have the debris going down the sink that people like to stuff down there that inevitably clog up the works. Also with no disposal, there will be a whole lot less vibration and movement of the plumbing.
I suffer from CDO ... Its like OCD, but in alphabetical order, LIKE IT SHOULD BE!!!