Question: I have water leaking behind the new hardy plank siding I just had installed. It is coming from the big pipe where the kitchen sink connects. It leaks on the outside of the house. Any suggestions?
Answer: It sounds like they drove a nail through a pipe when they installed the siding.
If you recently had it installed I suggest you call the contractor and have them repair the pipe and replace the siding.
If the installation is outside the warranty, you are either going to have to remove the siding or the plaster or drywall from the interior of the home to repair the damage to the pipe.