The best prevention is too keep your apartment temperature around 55 degrees. Even if you are away, don't lower the thermostat below 55. Open cabinet doors under sinks to allow air flow. If you have a history of freezing pipes, allowing a slow drip during the coldest days will keep the water moving and help prevent freezing. If you do have a frozen pipe, thaw slowly by having a space heater near the pipe. Thawing too quickly with a torch or een hair dryer can lead to expansion the the pipe bursting.