Prolonged temperatures below 32 degrees (6+hours) may result in ice forming inside your pipes. The exact time and temperature required will vary with wind and exposure of the water lines. To prevent damage from freezing, pipes should be wrapped in insulation made specifically for that purpose before cold weather arrives. 

Do not leave the water running overnight to avoid freezing.  You will be billed for the usage, and the City of Houston will not grant any adjustment.  If too many people run their water, the pressure can drop across an entire neighborhood, allowing contaminants into the lines.

If your house is going to be vacant and unheated all winter, it is recommended that you shut off the water at the private valve, then drain the hot water tank and all pipes.  You may wish to add an anti-freezing agent to any water remaining in toilet bowls. Use a liquid that has a strong color and odor for safety’s sake.