I have boon-docked for up to 3 nights at 15 to 17* temps. Other 3 nights were around 25*. I ran the house propane heater. No freeze ups. During the day around 40* ran the catalytic heater. Kept water heater running 24/7. The water pump is next to the water heater.
After reading posts about holding tank/wet bay heating I was curious about how the area was heated. Today (65*) I ran house heater on propane for 20 minutes and checked wet bay and fresh water tank area. I felt no heat or any breeze. No draft as checked with a narrow strip of tissue.
I have read posts saying passive heat going down through the vent holes in the bathroom heat tanks/wet bay, another post says small holes in duct send warm air to tanks, I'v always thought there was a vent some where from duct shooting heat to the tanks/wet bay.
Does any one know? However it is it seems to work i'd just really like to know how. My curiosity is killing me.