Cold weather holding tank heating

[Fletcher0077]

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.

[Phil G.]

Originally Posted by Fletcher0077

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.

In my 2005 Itasca Class C, the fresh water tank is within a large under area under the rear corner bed along with the water heater, water pump, and a bunch of fresh water plumbing. Also going right through this same area is one of the propane furnace's plastic plenums on it's way to the heated bathroom.

I'm assuming that in cold weather when we would normally be running the furnace that this plastic plenum - with it's warm surface - would be keeping the area under our bed and all the other items down there warm enough to keep the fresh water tank from freezing.

Winnebago may have implemented this design on purpose. However our motorhome does have the "winter package" option, which also includes 12 volt heating pads on the the grey and black water tanks. The routing of this warm air plenum under the bed may have been part of this package.

[Diesel-Lover]

winne with the winter pack have the 12 V pads for the waste tanks and there is a vent just like the one inside in the basement too. I recall seeing two of them one in front and one near the back. Those vents are always warm after a drive so engine heat gets there and furnace also provides warmth there, but the amount of air is rather low when on furnace. Temps are enough to keep from having to use the electrical pads. I also put in a vented 110 light fixture in the wet bay and also on the other side in the through compartment. There are low wattage bulbs in those metal and glass vented fixtures to allow the heat to escape into the basement, we turn them on when the temps are 25 or less. The water hose has the heat tape on it which kicks on at 35 or so automatically

[Edbehl]

We spent the past three weeks in Prescott and Sedona with a lot of snow and sub freezing nights

I had purchased a heating pad like you use to heat reptile aquariums and drilled a small hole through the fresh compartment water floor just large enough to pass the wire through and set it to 55 degrees to keep the compartment warmed enough

Worked great

[Class-C-Guy]

Originally Posted by Phil G.

In my 2005 Itasca Class C, the fresh water tank is within a large under area under the rear corner bed along with the water heater, water pump, and a bunch of fresh water plumbing. . . . However our motorhome does have the "winter package" option, which also includes 12 volt heating pads on the the grey and black water tanks. The routing of this warm air plenum under the bed may have been part of this package.

Duly noted and thanks for that!

[Morich]

One thing we've learned to watch is that there are things that freeze far quicker than the tanks. Tanks are big and often run along and under lots more floor as well as having lots more space for any expansion from freezing is less likely to break something. So if you are heating the tanks but leaving a bunch of lines running along near outside walls or underneath, you may still get caught with a real problem. Lines are small and have far less tolerant for freezing and expansion than the big tanks. Things like elbows which tend to have low spots where water may collect and stand can break pretty quick if we are not aware of the question.
Stay alert as nature is definitely looking for the chance to get to you!