Heated Water Tanks

For those of you that don’t have your fresh water / grey water inside your insulated space how are you heating / insulating your tanks. I see that there are some electric options but resistive electric is very power hungry, seems ill suited to off grid winter camping.
Fresh water inside heated envelope, no blackwater(composting toilet)
Gray water is outside, i did consider heating the tank, but the pads are very expensive and energy hungry. We leave the valve open in sub zero weather, If we are in a campground or any area that sees lots of use we put a 5 gal bucket under the drain.
So long as the tanks are within the insulated camper, the camper is heated, and you have adequate airflow between the living space and the tanks, no worries.

We have seen well below zero for weeks at a time, without any freezing issues in our custom hardside.

No black tank, but fresh and grey are both within the insulated camper.

For serious cold, electric heating is not the answer.

Gas rig, or on a budget, go propane.

Diesel truck with a good budget, look to diesel appliances, including furnace.
If one use hydronic heating, a simple loop thru the tank could work. Maybe not need much energy only needing to remain above freezing. Of course its all variable depends on tank size, insulation, location & environment.

Speak of freezing,
I wonder how tank shape can reduce damage by freezing. For example, tank walls all tapering narrower toward their bottom.
Stands to reason giving ice ability moving upward as it expands.
The problem with heating the tank is it is not just the tank. The drain hose and valve must be heated too. A well built steel tank will survive freezing if it is not full (the sides "oil can"), the couplings and valves are very prone to failure from freezing. Keep everything inside, this includes drain hoses and shut off valves (so you are now dealing with pump-out instead of drain), Keep the tank empty, or go south.
Actually, it is far better to keep the tank near full, rather than empty in severe cold.

The mass alone helps keep the tank from freezing.

It also helps maintain a consistent temperature cabin as well, again, due to its mass.

Also a reason to avoid metal plumbing all-together.

nylon fittings, polyethylene tubing, and PVC valves are far better with regards to severe cold than similar metal options.

Not only are they less likely to fracture if the water happens to freeze, but the plastic is simply MUCH less conductive to temperature changes than metal,
so they actually act as insulators, adding an added layer against the water freezing in the first place.
We are talking about tanks outside the heated envelope of the camper. The tank outside will do nothing for cabin temp. A full tank will take longer to freeze but it will freeze, the drain line and valve will freeze overnight( it has been below -10C here for the last 2 weeks). A full tank will almost certainly rupture if frozen, volume of contents increase by 10%. A frozen or partially frozen tank or drain means the loss of sinks,shower etc.
We did have 70l external unheated plastic black and grey tanks. We also tried to add hot water to both when it was cold out to try to maintain a higher average in the fluid.

But although the tank contents never froze the 2" of fluid above the gate valve but below the main body did.

We then mostly just put a decent size bucket under the open grey tank, tied up so it wouldn't blow away. The black tank needed attacking with a tent peg up into the gate valve a few times.

New camper will have a composting toilet, the grey tank will be inside and the valve for it will be too. Not sure what to do about the pipe connection through the floor yet though.
The new Revel Sprinter Camper From Winnebago uses the heated glycol tubing from the diesel heater to heat the tanks under the van. Seemed like a cool idea. There is a Facebook owners page if you wanted to hear real world experiences with that system.
Frac water heaters play an important role in the hydraulic fracturing process. Fracing solution is generally stored at ambient temperature but needs to be heated before it can be pumped into the ground. Frac water heaters are used to circulate large amounts of water and fluid and gradually heat it to optimal fracing temperatures. Because propane is the fuel source running the frac water heater, it is extremely important to maintain propane tank pressure. Power blanket solves this problem by designing custom, truck-mounted tank heaters.