If your pipes are gray (you didn't give us a brand, model, or year of your RV), then that's the old style PEX and it sucks. All the big box home improvement stores now carry the white PEX...much better stuff. You can cut it with a standard copper tubing cutter, the couplings are easy to use, you can bend it around a 90° angle using a plastic snap on holder, and it's resistant to freezing. The couplings join up the old and new PEX types without problems (except getting a good cut on the old PEX with a hacksaw - but a plastic tubing cutter works). I find all the parts needed at Home Depot, Lowe's, and Ace.
You'll like the new PEX stuff.