When on Vacation and away from home you can set your furnace thermostat to 50 F so it will keep your house above freezing and to prevent the potential of frozen pipes.
Never lower your furnace thermostat lower than 50 F or turn your furnace completely off while gone because you could come back to frozen and burst pipes along with water damage to your home.
Keep the thermostat at 50 F and your water pipes should be just fine.
The furnace will come on when the temperature in the home gets below 50 F and then turn back off when the temperature rises again to 50 F.