Unfortunately in my recently purchased 2014 Impala LT (new body style) there's water getting into my trunk and even into my back seat floor boards. I've determined that the rear tail light gaskets do fail prematurely and allow water seepage all into my vehicle. Well I've purchased the new gaskets and they're enroute, however I am at a loss how water from the tail lights could possibly get into my rear seat floor boards. And honestly, I wouldn't think that it could at all. The areas just seem to disconnected in location spots. So, just to check and make sure that damage from my car being totaled, isn't allowing water leakage from the sunroof pipes, I'm just trying to cover all basis. Unbelievably there was so much water in my rear floor board that mold started growing. I caught it very quickly thereafter, but I'm seriously needing to resolve this issue fast as humanly possible. Thanks for any info related to this.
There was a recent post on this forum by a member with the 9th generation Impala, and how he cleaned the sunroofs drains - and their location.
You may want to do a search.
EDIT: Here is a link: Sunroof Drain Tube Clogged