Michelle, you are SO right. Thankfully, electrical and electronic stuff is something I feel comfortable with - I generally know how to make the 'trons go where I want. Now plumbing, yuch! That stinkin' (sometimes literally) water ALWAYS finds my mistake.
I got 14/3, it's rated to 15A - my 1500w heater draws 12.5 amps, so that should work. I also got 20A rated outlets. Although I may just go back and get the 12/3 - a few more $$ is cheaper than a new trailer! Y'know though, the weird thing is that the heaters themselves use wire that's smaller than 14, AND they don't have a 3-prong plug.
And I think I might've found an answer to my original question. Here's a link for anyone interested:
http://www.mygreathome.com/fix-it_guide/heat_tape.htm
It says to use thermostatically controlled heat tape. Duh JP!!! I can just set it to a reasonable temp so it won't hurt the lines. I'll give this a closer look.
So you're in the Finger Lakes area. An old girlfriend lived in Newark, and on one visit she took me to an amusement park somewhere in there. Me, I'm down next to the Chesapeake Bay.