If you leave the heat on, and its reliable. They just shut off water, leave temp at minimum and pipes shouldn't freeze if installed properly.
Otherwise everything needs to be drained. This is most easily done if the pluming is designed for draining. I suspect its not.
For supply - You would need to identify every low spot in the system and install a valve to open to gravity drain everything. Don't forget the water in the toilet tank, and well pumps, tanks, etc.
For waste - You will need to remove all traps or fill them with antifreeze. If you remove a trap you will want to cap it or stuff a rag into it to prevent sewer gas from entering building.
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