Bathroom sink replacement
#1

I am replacing my bathroom sink and vanity. When I removed the drain pipe, I noticed that it is covered in "guck" for lack of a better word. The water inside of the main pipe is cloudy. Is this normal? I always thought that the water smelled funny. Should I be concerned?
#2

The gunk is mildew, soap scum, and anything else that has passed down that drain. The water can be cloudy from a number of things and that is why it is in the drain. This is the reason why p-traps are on drains so these smells do not enter our homes. Plug the drain until you get your new drain on. If the drain runs freely after replacement you have no problems.