Depends- what do you have for a RV?
I am sure there are lost of opinions and solutions, So far, mine has all the FW pipes contained within the heated spaces of the MH. Except for external shower- not sure what to do with that. May put insulation around the taps and hope for the best- I wish there were turn offs inside the coach for those lines (may add them). The 2 holding tanks are exposed. I do have 12V heated pads on those (and I sprayed approx 1" of foam all over the tanks and pipes Problem is, if you do not have a hook-up for juice (or a genny) you can deplete the batteries using the heating pads. Some people winterize their system and bring water, dump water outside, etc. Some even flush their toilet with pink stuff if really cold.
It all depends on your set up, what you need to do to make it better, and if you have hook ups and or need to use plumbing.
If the weather gets cold, I do have my small compressor and we can easily blow out the lines. Then when warms up we start using again....
2015 Coachmen Prism 24J MBS