Dang! Sloppy writing on my part.  Thank you for the correction. 

Sorry to point this out Happy but turning on your hot water heater with the tank empty will not burn out the anode rod. The anode rod is just a sacrificial metal rod of aluminum or magnesium. What will burn out is the hot water heater element if the tank is not full of water.

To expand on the above, the only sure way to check whether the water heater is full before turning it on is to use the pressure relief  valve outside behind the cover. If you pull the handle on it and water comes out when the pump is on or city water is connected, you can be sure it is full. If air comes out, it isn't. If nothing happens, it is likely bypassed.

One can remove the anode rod to ensure it is empty. If so, use the pressure relief valve to make sure all the pressure is released before removing the anode rod so the rod isn't blown a significant distance from the 'Pod.

I want to quietly address two things here..

1) getting water out of the HW tap doesn't, ever, mean the WH has water in it. Getting HOT water out of it does. If the WH is in bypass mode, then water in the HW lines just bypasses the WH, still comes out of the taps. This is a common misconception about how the system works.

2) The only worry about freezing the lines.. is actually about freezing the fixtures. The R-Pod is plumbed entirely with PEX. The only leaks or damage to the PEX lines we have ever had reported is when factory workers inadvertently staple or put a screw through a line.

Come spring, the things broken will be.. toilet valves, outside showers, and water pump filter housings. So far, I don't remember anyone in this group losing a water heater or it's fittings. But, it won't be water lines.

Nothing in the Pod is going to freeze if the air temp outside gets to 27° F for a few hours.  If I were worried about freezing in your circumstances, and shore power wasn't available, I'd set the furnace to come on as low as possible and remove the inside kick panels in front of the water heater and water pump and I'd leave the bathroom door open.  (I'd leave a little electric heater set as low as possible if I had shore power, and to the same.)  

It is an absolute no-no to turn on the electric element of the water heater without the water heater being full of water.  Doing so will almost instantly fry the heating element.  Not so much with the gas, although still not a great idea probably. 

TT

I believe that if you use your water pump and get water out of your hot water faucet, you will have enough water to avoid burning up your anode. (Someone will be sure to correct me if this is wrong .)

More importantly - As a 'Newbie' I will share some thoughts with you. I am apparently a small minority here in having a great respect for the power of expanding ice over time on rv pipe connections, rock surfaces, or anywhere else. 

I am reasonably sure that Furpod and others are correct in that there will be no obvious harm in having unwinterized pipes freeze once. What bothers me is that the freezing water expands, and that can't be without harm, however small, and that harm will accumulate with multiple freeze-thaw cycles until it no longer is unnoticeable. Otherwise we wouldn't have to ever winterize. 

Altho I too have inadvertantly experienced overnight hi-20 temps, once, without antifreeze and without obvious damage, for that reason I always winterize and I urge you to do the same.

Originally posted by Mbearden I was instructed to never run the WH unless I was sure it was full of water.

Well.. we can only go by the information you give.. Since you were concerned specifically about the WH, I figured you had water in it. If it's empty, then there is no water to freeze, so it can't be damaged. 

WH can't freeze if it's on....

27F overnight with 50's during the day is no issue.

The low temp for the next two nights is 27...50 in the daytime.

Would running the heater in a closed up unit keep things warm enough....also concerned about the hot water heater.

 One night on the way home we will be staying with a friend outside Atpants...same weather forecast.

Thanks for your help.