This storm has been horrible on peace of mind. As we thaw out, the house is making all kinds of pops and creaks. To ease some of the minds out there, I had a knocking sound in the floor every time I ran the hot water in a specific sink this morning and yesterday morning. Run the cold in the same sink, nothing. Check the meter, no spin, so no leaks, even after the thaw yesterday. Asked my plumber buddy about it. Thermal expansion. Those drain pipes are along the outside wall and cold as hell. When the hot water runs through them, they undergo thermal expansion and make the knocking sound that echos all the way up the pipe. So anyone out there that hears the knocking sound only when they run hot water at a specific sink, keep monitoring it, but it could be thermal expansion and nothing more. It will go away when the temps normalize.