Thank you very much for all your comments and advices!
I am from Quebec only 15 minutes north from the US border (Vermont & Maine).
Tonight I'll take a few minutes and blow the fresh water pipes because I have the blow-off adapter already and it only take a few minutes, but I'll not touch on the bath and kitchen sink drain yet and I'll connect and install my small ceramic electric heater set at 5'C tonight, just in case... I'll open the cabinets door to make warm air to circulate everywhere there's water pipes. I'll also drain the water heater because it only took a minutes to do. Fresh water tank is already empty so as the gray and black tanks.
FYI I use a mini oil circulation space heater (25$ Walmart) when we are camping with the trailer, this thing is just amazing because it take very low power (700W, so safe on small RV circuit) and because of the mineral oil (sealed, close circuit), it come pretty hot (still safe against burn) and stay hot for a while after the heating element turn off. But the best part is it doesn't do ANY noise at all (ZERO!!) like ceramic space heater and it doesn't do any light during the night like halogen heater. But during the storage I'll use my Honeywell ceramic heater because it's easier to setup because it already have the "anti-freeze" function on the thermostat.
