You have two sets of pipes, Fresh and waste.. Waste water is normally "Contaminated" and generally contaminating water LOWWERS the freezing point so odds are you are safe there.
Fresh water pipes are internal and thus heated to some extent and for that little bit below freezing likewise good there.. Pipes in RV's nearly never burst due to freezing, Connectors however are another story, they do not have give in them.
how to tell if the pipes are leaking... Method one (The easy method)
If you have water in your fresh tank, turn on the water pump, turn off (not in yoru case already done) the outside supply, and usually the pump will run a bit, depending on the pressure in the system anywhere from a second to several minutes.. Then stop. If it stops, and stays stopped. You have no leaks.