Reddit reviews Easy Heat AHB-019 Cold Weather Valve and Pipe Heating Cable, 9 feet

Antifreeze in non potable lines/pipes. If you are docked and have AC electric service use heat tape. http://www.amazon.com/Easy-Heat-AHB-019-Weather-Heating/dp/B00002N6MB Also an incandescent light bulb of a decent wattage in the compartments where the lines are will most likely work. Heating a water tank is pretty easy. Remember you need to keep it a few degrees above freezing and it doesn't need to be hot. I've thought about using a few scraps of heat mat that is used under tile floors and throwing it on a tank.

Obviously it is a little late now, but with these backflow preventers, you will want to "winterize" them in the fall/winter. Each model is different, but with mine, I remove all the internals and drain what water I can in there. After that, I use heat tape (http://www.amazon.com/Easy-Heat-AHB-019-Weather-Heating/dp/B00002N6MB/ref=sr_1_2?ie=UTF8&qid=1397143706&sr=8-2&keywords=heat+tape) and wrap the pipes with it. The manufacturer suggests blowing all the water out of the lines with an air compressor, but I have never done it. I keep it covered with an trash can (it's in the side yard not visible to anyone who isn't going over to that side for a reason), but you can also use one of those fake rocks (http://www.amazon.com/Orbit-Watermaster-53016-Granite-Sprinkler/dp/B0013I2MSG/ref=sr_1_1?ie=UTF8&qid=1397143834&sr=8-1&keywords=fake+rock).

Anyways, for your current issue, I would google the model # and look for repair kits. For my model, you can buy that plastic cap and the internals. Replacing it was a breeze, but it may be different for your model.

I know many lawn / sprinkler service companies would love to have the privilege to come winterize your system and then prepare it in the spring, but it isn't an awful task at all.

Good luck..

A search on Amazon turned up one result

This should do the job for you easily.

When I was in Colorado last winter (where we had a storm that brought some days with a HIGH of 15, and a low of -25) I used:

Fresh water line

Heat tape

Self-adhesive water pipe insulation

40* Auto-on electric doodad with three outlets.

• Plug the Heat Tape into the outlet inside the wet bay - run an extension to the wet bay if you don't already have power there.
  
• Put the heat tape inside the foam insulation with the fresh water hose with the heat tape away from the split as much as possible. Optionally, you can wrap the hose and tape with aluminum foil as a heat conductor. Seal with the split with duct tape. I found the factory stick on the insulation to be not enough to reliably hold.
  
• Wrap the excess heat tape around the pedestal to keep it from freezing.
  
• Cover with a bucket, weigh with a brick.
  
  Water Bay
  
  Inexpensive Hanging Trouble Light
  
  Generous supply of lightbulbs.
  
  
• Put a 75-100 watt bulb in the light.
  
• Plug the light into the thermocouple outlet.
  
• Turn the light on and hang it someplace.
  
• Check it periodically to make sure the bulb still works. I went through 4 bulbs in a month.
  
  Tanks
  This is harder. They do make heated tank pads, but unless you're invested long-term in your current RV, AND in staying in colder climates? Enh.
  The best inexpensive solution I've seen is one that you can take advantage of right now, if you can find them in the store still - probably on clearance.
  
  See if you can find a couple long strings of incandescent C7 or C9-style christmas lights. Plug 'em in on a timer or another thermocouple outlet and arrange them on the ground underneath where your tanks are. Once you put up the foam board, the heat from the lights should keep the underbelly above freezing...