Yes, you risk damaging the water lines. The risk is directly proportional to how cold it gets for how long. Even 30° for one hour can freeze those tiny lines. Will that damage them? Who knows. How about providing some supplemental heat, or blowing out the lines but no antifreeze? Or just wing it. The risk is pretty low, but the other side of the coin is it could result in hidden damage that causes big problems like delamination down the road. No easy answer. Easy for me to say take a chance cause it ain't mine to pay to fix down the road. So do you feel lucky today?