loud "knock" heard and now water trickle

Hello: I am not sure these two incidents are related, however, it seems that I now have a trickle of water 24 hours a day. The trickle is inside a copper pipe that is located inside the pipe that holds my washer hose. I don't know where the water could be coming from. I checked the washer hose, and the water is not coming from there. The pipe right next to the hose is a pipe within a pipe. Weird...it is copper and attaches to the wall...straight up.

SOOOO....does anyone know 1. Where is the water coming from?
2. What is this copper pipe used for?
Thanks, Madge

Pictures would help. With the copper pipe it almost sounds like a condensate line. If it is there is a possibility that it is a secondary drain if you've never noticed anything coming out of it.

Do you have an air handler around there?