With colder overnight temperatures upon us we recommend covering your backflow (and the above ground pipes connected to it) with a blanket any time the weather is expected to get below freezing if your system has not been blown out yet.
If you are unsure what the backflow is, see the picture above.  The pipes attatched to it could be copper, PVC (hard white plastic), or poly (softer black plastic).  The backflow will be located somewhere on the outside of your house, often but not always near where phone, cable, and gas come into the house or near the dryer vent or air conditioner.