hurricane 2007 34n motorhome

My guess is your "heated" tanks are actually passively heated with some residual heat from the furnace ductwork and not actually actively heated. If it gets above freezing during the day I would imagine that a full FW tank would not freeze. I also suspect it may not be your tank as much as your lines and pump. The issue with heat tape is you never know when it stops working. Usually light bulbs in wet bays are enough to prevent freezing but 13 degrees is pretty cold. Opening your cabinets and allowing heat to hit the plumbing also helps. But camping in 13 degree temps without a rig designed for it is prolonging the inevitable. When we would camp in temps that cold we would winterize and use the CG restrooms. I've had my water pump freeze more than a few times, even with a light bulb.

If we are out in what might be freezing weather, I carry two clamp on work lights that I put inside the bis with the water tank and waste tanks. I also have a remote thermometer in the bin so I can monitor the temps inside without haveing to open the bin door. I usuall have 60 watt bulbs in the lamps, which has been fine so far, but 75 watt bulbs work even better. With outside temps in the low 20s, bin temps usually stay in the 40s or 50s. Works for us. Outside shower tubing is actually inside the wall, but I usually drain it anyway. If winterized, I always have pink stuff in the outside shower, so that usually in in it all year long. We started out with a 1999 Hurricane, but after putting 50K miles on it we traded up a bit.

Was your RV plugged in? Was the tank heater switched on?