Cold Weather Camping - How cold is too cold?

Having overnighted many many times while on the road with NO electric hookup, I can reccomend from real world experiance that 25 degree overnight temperatures with NO, again NO additional heat duruing the night poses absolutely NO problems in the morning. The 25 degree temp has to be at the level for all of the overnight hours before any residual slush/freezing of non-anti freeze protected water will be affected. If you are staying in a fixed location, that is to say not move the next day or two or three with daytime temps at the 25 degree mark and non use of the unit, then in my experiance where the daytime temps did hover at just above freezing then dropped to the nightime temp of at the lowest 25 degrees, the unprotected water in the water heater as well as the water in the water lines did get slushy where the water pump could not move water. The non use period was for 4 days with the temperatures as stated. Once heat was added to the motorhome the non movement of water was eliminated after 4 to 6 hours and no pipe damage resulted. All units are not the same. One experiance for an owner may not be dupliated by another with the same unit. I respond to the poster to affirm what others have already indicated. I agree that 25 degree overnight low temperature will not create a problem for a unit that is IN USE even if the motorhome/trailer has no additional overnight heat.