clicking sound inside the wall after using water

Clicking sounds in wall when water is used is most frequently expansion of pipes as you found out. Try running cold water into a bucket and listen for clicks. Then try hot water in bucket. Now dump the water into the drain, does that make clicks?

You do have options here. If it really bothers you then open up the drywall and strap the drain down with pipe straps. Good luck. Tom

Both hot and cold water will make the click happen, but hot water will make it come faster. Once the click starts, the more water I use, the more frequent the click sounds. After I stop using water, it takes around 10 minutes or so for the click gone. Is it normal?

Hi, I have a two-story flat roof house, as I asked in another question, every time I use the hot water in the second floor bathroom, I will get water dripping sound inside the wall somewhere up high close to the roof. I was told it might because of the contraction and expansion of the pipe due to the temprature change. I tend to believe it is true because I don't see any wet sign on the wall or the floor. But I'm just curious that is there any pipe contains water possible to have leak at that place? Thank you for your help.