Clicking sound inside the wall after using water
	
	
		Hi there - I'm having a very annoying problem. Every time after someone uses the water in my second floor bathroom, I will get clicking sound inside the wall between the bathroom and my bedroom. And the sound seems coming from the top close to the roof. At the place, I guess there is only the vent(correct me if I'm wrong). I saw some people got the similar problem and it's due to the expansion and contracting of the pipe. I don't see any water sign on my ceiling or the floor, so I prefer this answer. But just wondering right now the weather is pretty hot already, why I still get this problem and every time it happens, it seems last longer than before. It might not a big deal, but really annoying. I appreciate if anyone could help. Thanks!