Congrats on your SMB and welcome😊
Some additional info will help to get answers -
What type SMB do you have? E350, Sprinter? Layout ? Year?
Do you have a cabin heater? Eg Espar or Suburban?
Where is your water tank located?
Hot water system? Type?
How much time will you be in the van during your trip? Will it be unattended for some periods?
Battery bank size?
For our winter trips - if the van is going to be unattended for a couple of days, I will usually drain the tanks to be safe. If only a day or so, and solar available, I will run the Espar heater which is on a thermostat. In all cases the exterior shower hoses are drained and the valves to the shower are shut off.
Beastie 3: 2002 7.3 EB Cargo: Agile TTB, CCV Mid Top, Custom Walk Through, Lots of stuff added. BlingMyRig.com