Kathy noticed a dark spot on the ceiling of the guest room this morning. I checked it out and it was definitely caused by water. The HVAC unit is right above the spot and its a little hard to see the ceiling from the top side because directly above the stain is an OSB floor for the HVAC unit and the hot water heater. The hot water heater is definitely not the source of the water nor does it appear the water is coming from the roof above. The water drain pan under the AC unit hasn't been wet. I think the water is leaking out the condensation line that leads to the sink in the bath next to the guest room. I'm not sure that it's actually leaking out of the PVC pipe however. It was wrapped in that black rubber pipe insulation and there was water between the pipe and the insulation. I pulled the insulation off for several feet and there was a dark stain on the OSB under the pipe. I've never seen one of these lines insulated before. Could it be condensation being trapped between the pipe and insulation instead of an actual leak in the pipe?