Are you sure you have heated tanks? Coachmen does (or did) not offer that option as far as I know. I don't think you can get heated tanks even on the Diesel line from Coachmen (Forest River). Someone may comment that heated tanks in the diesel line are now available, I don't know.
I have an Encounter (2011) which was offered as their top of the line gas coach in that year (and since I think) and it does not have heated tanks nor was there an option for heated tanks. It is a three season coach.
I did look at retro fitting tank heaters and the cost was prohibitive. There is no furnace ducting to the tank area or to the wet bay. FYI you will have a freezing problem in the wet bay before you have a tank freeze.
We got caught out in 28 degree weather one trip in March this year (2014). If you are caught in cold temps my advice is to run your furnace up to a higher heat setting than you might otherwise use, pull your slides in to conserve heat, and put a portable light (incandescent or halogen) in your wet bay. That should generate enough heat to keep the water lines in that enclosure from freezing.
Good luck; freezing pipes is not something you want to have to deal with.
Gary, Cindy, Reacher (Maine Coon), and Vivian (in spirit only now).
Retired: July 31st, 2013 and loving it.
2011 Coachmen Encounter 37 TZ pulling a 2012 Wrangler Unlimited Sahara. Many upgrades, additions, mods, and changes.