Supplemental heat to "basement"

jholovacs wrote:
I fulltime RV, and in the winter, if the temp outside gets below 15F, my kitchen sink lines freeze, even with the heated, enclosed underbelly.

Does anyone know a good product or method for adding a bit more heat to the underbelly that I can wire in in a more or less permanent way? I'd like to flip a switch on cold days and not worry about the matter any more.

I have a spare 110V circuit since I switched to a tankless water heater, so I am perfectly ok with electric, but it needs to be safe, since it's not something I'm going to be able to monitor easily.

Thanks!